Although in the first days of opening an account , depositing an amount of money and paying for one or two things from the account it will have very little information to work on to give you an accurate “summary” of your spending until it knows your committed spends , your “average” daily purchases etc etc
As far as I understand - you deposited £10 a couple of days ago , some of which you presumably spent , that will become your average daily spend as you have very little spending history to work on ??? you’ve then added more money , when it said “you had £36 left” over that was a day earlier from the “you will have £44 left over” - maybe you haven’t spent anything from yesterday to today but the number of days has decreased until the end of your summary period, yet your balance hasn’t moved and your average spend hasn’t changed, albeit over one more day average ???
So based on your average spend , the account balance , your committed spending (none as yet ? ) and the number of days left you will have £44 left over , tomorrow if you dont spend anything I would expect to have somewhere near £52 left over - as your average daily spend will have changed slightly because of the extra day , always assuming you have more than the £52 in the account.
Clear as mud