State Pension & Self Assessment Return

I am completing 23/24 self assessment. I understand that I need to put details of the state pension I receive on the SA. How do I identify the exact amount for 23/24. I can put the 4 weekly payment (x 13) in but there was a pension increase was calculated from 10/4/23 so that multiplication wouldn't quite align with what I receive. Do I just submit on 13 x 4 weekly amount? Why can't HMRC pre-populate this box as they do with income I receive from PAYE employment that I continue to receive

Hi,  HMRC usually receive State Pension information from DWP but in the absence of this please complete with the information you hold.

The document "How to fill in your tax return" downloadable from https://www.gov.uk/government/publications/self-assessment-tax-return-sa100 tells you at the end of page 6 and start of page 7, to calculate the amount as 1 week of the old weekly amount plus 51 weeks of the new weekly amount, in most cases.