Does form 1099-R for Military Retirement from my ex husband belong in the first box 1099-R income or the second box. It gives me a refund of $600.

*I just don't know where to post this.  I've had this form 1099-R for years.
If I enter it in the first box, that is where it gives me the extra refund.  If I enter it in the second box, then the $600 goes away.