Travel Days

with the 7d in 1M pass you can travel under use of the pass on 7 days to choose by you. for the 8th day check out which leg is the cheapest by normal ticket and buy that instead of using a travel day there.

So am I correct in thinking I have purchased Reservations for 8 days on  my trip but before travel I have to asign 7 of these days to the pass and then just purchase a ticket to match the 8th reservation

When you travel in Switzerland you don't need any reservations, reservations in Switzerland are a waste of money. Just enter the train as a journey in the Railplanner and activate it just before boarding the train. 

​@Pdaddy 

If you have mandatory reservations for long distance trains (e.g.TGV in France, Frecciarossa in Italy or Eurocity between Switzerland and Italy), you must use a travel day of your pass. It is not possible to buy only a ticket for these reservations.

You can also consider doing the sums and seeing whether it makes sense (or is possible, depending on whether you bought it in a sale, etc . . .) to up your pass to the next level - probably 10 days.

To be clear . . . this would mean cancelling/refunding your existing pass and buying a new one.

Usually the other way around: if you first buy a new one ad the request a refund of the old one, then it's treated as an exchange, with a lower fee.