What is 2021 RRSP/PRPP/SPP deduction limit including eligible transfers? The box next to it shows 55k . I don’t know what it is or what to do for the next boxes.

As per this Canada Revenue Agency (CRA) webpage – Definitions for RRSPs, your RRSP deduction limit is:

The maximum amount you can deduct from contributions you made to your RRSP, PRPP, SPP and to your spouse’s or common law partner’s RRSP or SPP for a year (excluding transfers to your RRSPs of certain types of qualifying income). The calculation is based, in part, on your earned income in the previous year. Pension adjustments (PA), past service pension adjustments (PSPA), Pension adjustment reversals (PAR), and your unused RRSP deduction room at the end of the previous year are also used to calculate the limit.