There is no individual refund amount on a joint tax return. Everything is combined and there is only one refund calculation. The refund belongs to both of you jointly. The calculation of the refund is based on your total combined income, the amount of tax that the two of you together have to pay on that combined income, and the total combined amount of tax that you paid through withholding or estimated tax payments. It is not calculated separately for each person.
Why are you trying to figure out individual refund amounts? If you are trying to divide the refund between you, you can split it in any way that seems fair to the two of you.
