Thanks a lot for the explanation. I see similar amount in Box 52 but assuming that it's the employer's contribution which is exactly 100% and about which I am assuming I do not need to do anything. If my contribution on T4 then it could be under which box.

Also for changes in 2022 return to incorporate the previously missed Jan-Feb 23 contributions, do I need to re file or just submit schedule 7. Any guidance would be highly appreciated!

Yes, Box 52 on the T4 is The pension adjustment (PA) amount  which is the value of the benefits you earned in 2023 under your employer's registered pension plans (RPP) and deferred profit sharing plans (DPSP), and possibly some unregistered retirement plans or arrangements.

If you do a Refile it will send the schedule 7 to the CRA online, with your changes.