Foreign Tax Credit, when does HMRC calculate it?

i am in the process of competing my self assessment return for 23/24 online. I have dividends on foreign shares and want to claim foreign tax credit relief but the following comes up when I click on 'View your calculation'. "Sorry, we can't automatically calculate foreign credit relief for you. If you wish to work it out for yourself the figures below will help you." I find it too confusing to work it out for myself, so please can you tell me how long after submitting my return does HMRC calculate the foreign tax credit relief? Also, I think I will have paid too much tax without it being calculated before I submit my return, so will I get a refund once HMRC calculates it? Thank you

Hi,
As it is online, HMRC will not look at it and you will need to contact us once it is submitted and ask for a review, any refund due would be issued at that point.
Thank you.