Total to be added - showing in Tax calculation

I am just completing my self assessment form for 2022-2023. I do not understand the amounts shown - can someone explain the following example. If my total tax owed amounts to, say £1500, the first payment duse will show £750.00 by January 2024 with a second payment of £750 showing due in July 2024 . So far, so good. But why is there a figure showing under the heading "Total to be added to Self Assessment account due by 31 January 2024" which is quite a bit higher than the £1500 due according to the tax calculation ??? Can someone explain this simply as I do not know what amount to pay by Jan 31st 2024. Will this "overpayment" ever be credited back to me ??

Hi barryman,
Based on your figures, the payment to be made in January 2024 will be £2250 - the balancing payment of £1500 for 22/23 plus the first payment on account of £750 for 23/24.
Once your submit the return for 23/24 and the payments on account are too high, these will be adjusted accordingly and any repayment issued where applicable.
Thank you.