As you live in the UK you can only use the pass for 2 travels on the Eurostar, no matter for how many days the pass is valid. The outbound/inbound rule says that you can travel on a maximum of 2 travel days in your country of residence.

For children age 4-11 you can get a free children's pass when you buy an adult pass. The child needs the same reservation as an adult.

Hi Anna thanks for your reply. Yes my daughter has a pass too. Why does it said 4 trips then? I  bought the pass for almost 280 euros and my trip to Paris cost my £60. So if I can only use this pass for 2 trips there's no profit then  

That means you have not used any travel days and not any outbound/inbound journeys either.

AFAIK Eurostar don't have season tickets, only a frequent traveller programme.

It is clear in the conditions of Interrail that you only have 2 travel days in your country of residence. The idea with Interrail is not to travel in your own country, but to explore other countries in Europe. 

Have you already travelled to Paris once?

But I have used my pass in Jan with Eurostar though. The thing is Eurostar told me that I have to always come to the station to book for my trip and collect my ticket 

Anna, you don't get it. I live in UK and I bought the pass to be able to travel to Paris every month on a affordable prices.  Yes i have travelled to Paris on the 5th of Jan and came back on the 8th of Jan

There is no need to get your seat reservation from St Pancras, you better make the reservation on line at b-europe. Please read more below. 

There is a limited number of pass holder seats on the Eurostar and on popular departures and during high season those sell out weeks, and sometimes months in advance.

The best place to see the availability of passholder seats and make reservations on the Eurostar is 

https://www.b-europe.com/EN/Booking/Pass#TravelWish

If you don't get any result, press "later trains" and eventually you will find the next available connection. 

If you have a mobile pass you need to generate a Pass Cover Number in order to make the reservation at b-europe. You do that here in the PCN generator:

https://community.eurail.com/news-and-announcements-39/pass-cover-number-generator-is-live-5653

Then you didn't activate the mobile pass correctly for your trip to Paris. If you would have activated the pass then you should have used 2 travel days and both the outbound and inbound travel day.

Strange that you were able to travel on the Eurostar without an active travel day. 

In St Pancras all they asked was my pass reference number and they did everything for me. Hence I'm a bit confused . And there's no customer service to call regarding all my inquiries. 

Interrail passes are intended for travellers outside their country of residence. A few years ago they added the facility to use it in your COR for any 2 of the travel days allowed by your pass, if you wanted to. The majority of pass users that use them do so for helping to get in and or out of their COR, but if and how you use them is up to you.

It would seem your first trip was actually not facilitated by your pass, but by standard tickets from Eurostar, as each time you use your pass it automatically takes one of your 4 days and certainly using Eurostar it would take one of your COR days (They call them In/Out days.

This COR rule is absolute - only a max of 2 days irrespective of the length or type of Global Pass.

OOI a 4 days in a month pass allows you 4 days of your choice from the day you start travelling for one month, simply calculated as e.g. 10 June - 9 July.

Eurostar often only check the reservation, I heard that a number of times. But sometimes they also check the pass.

Eurostar only check your pass number then proceed for payment. I have tried since yesterday to purchase a ticket on b-europe but it did not recognised my pass number. I'm giving up

I meant when you are travelling.

B-Europe want a pass cover number, which is on the cover of a paper pass. If you have a mobile pass, you can generate one from your mobile pass number:

I know Interrail tries hard to explain the difference between reservations and your valid ticket to travel but it still confuses many.

In the simplest terms I can manage this is my explanation.

To travel on any valid train not requiring a mandatory reservation you need to add each individual train to your trip (either from the planner or manually) and then before boarding you simply add it to your pass by operating the slider against that train in your Trip. The first train of the travel day creates a QR code and a list below the QR code of the train details (subsequent trains on the same day are added to the list as you transfer them. This is now your valid ticket to travel on that train, and is all the inspector requires to see. (estimates say this is about 90% of all trains).

If a train requires a mandatory reservation (the other 10%) this is completely separate from your pass. There are many guides on acquiring these.

To travel on these trains you will need both some form of proof of reservation AND a valid pass/ticket as shown above. Both these are required to travel on that train, but depending on the inspector they may simply check the reservation, but that is by no means always the case. For example Eurostar will usually allow you into the lounge/waiting area on the reservation without proof of your pass, but an on train inspection may be more likely to check your pass than your reservation.

In the majority of cases inspectors will accept a show of a pdf file as a valid reservation, but technically some say you should print it out.