On3and6
Does the system effectively fwd calculate (assuming you/I complete the RoS or, does it give a true and accurate amount on the day?
I think it is an on the day calculation as there is no way of the system knowing how long you plan to serve for, although the pension itself (rather than EDP) will be calculated from your State Pension Age. The best thing you can do is run the figures through the MOD pension calculator and set your planned exit date to a realistic point in the future - you can then use the sliding scale to see when any major changes might occur. The online calculator will give you a good indication but not an exact answer, as everyone's circumstances are slightly different.
The Forces Pension Society will give you more professional information and it is always worth consulting them. FPS cannot give you advice though, you need an IFA for that.