1. Did you file 2022?
2. Is 2023 is the first year you file your T1?
Line 24500 is the total contribution you made and whether they were contribution between first 60 days of the year. Your 2024 contributions were in that category. This amount can be deducted on your 2023 T1 and if you prefer, you can leave it for later years.
The second type is between Mar 1 to Dec 31 of the year (2023 in your case) You can deduct these on your 2023 T1 or leave it for later year.
Line 20800 is the amount you WANT to deduct on your 2023 T1. You can choose NOT to deduct the full amount and leave the rest for future
years. If your income was not high enough, my suggestion is to leave most if not all for future years. Check out the marginal tax rate and see how much deduction would put your back to a lower marginal rate.
https://www.wealthsimple.com/en-ca/tool/tax-calculator/ontario
Contribution amount
The amount of contributions made, in dollars and cents, for the contribution periods noted above.
See Schedule 7 to find out if you have to complete this schedule for unused contributions, transfers, withdrawals and repayments under the Home Buyers’ Plan (HBP) and the Lifelong Learning Plan (LLP).
Otherwise, enter on line 24500 the total RRSP contributions made for both contribution periods noted above and enter on line 20800 your RRSP deduction you want to claim.