My GBP Flexible savings interest has halved!!

I am trying to understand the binance gbp flexible savings product.

I made some money in bitcoin and had a gbp balance of £500000

So I decided to leave it in the savings account

£500000/100*5% = £25000 / 365 equals interest which was fine. I was getting £68.49 a day.

Then I brought some eth and my balance went down to £479500

The Interest was correctly worked out again. About £65.67 which is also correct.

Then I noticed the apy changed to 4.68% and my interest went down to £36.13

Then the following day it went to 4.36% and again the interest paid was £36.15

By my calculations and looking at the above it should be £479436.52/100*5 = £20903.43 /365 should be £57.26

But I am getting way less at £36.13

Not sure how they are working this out seems strange. Still more than I would get with my bank but just trying to see how it is worked out....

Any help please as I was using this interest to buy crypto daily and it was a nice chunk which seems to be halved now?

Thanks for reading and understanding.