IRSclaimed it will be put towards previous year debt.Currently,the old debt is lower than whatIRS should have paid me for 2024.How long does it take for they balance?

Even if you have been on a payment plan for the back taxes, your 2024 refund will be offset to pay toward the amount you still owe.   If there is a small difference between the amount owed and the amount of your refund, you will eventually get that small amount.  Remember that the amount you have owed is subject to interest as well.   The IRS will send you a letter when your tax debt has been fully paid and will issue a deposit or a check to reconcile the difference if anything is still owed to you.  It sounds like the difference that might still be owed to you is pretty small.

Watch your online account with the IRS

https://www.irs.gov/payments/your-online-account