I have had final salary membership (pre 1 April 2015) for 10 years – why does it only show 5 years’ membership?

If you worked part-time, before 1 April 2015, the membership shown has been adjusted accordingly. E.g. if you work 20 hours per week (full-time is 40 hours) for 10 years you will build up 5 years’ membership in the Scheme.