I feel this is like a word problem without all the details. For instance, was that payout to her after the mortgage transferred or refi, or did her mortgage get paid off or did she need to send in that amount to pay off that mortgage? Was the FMV of the property in the computation of the division of marital property, and she is forgetting, such as, "Okay, you keep the main residence worth $550,000 and half in debt, and he gets the rental at $557,000 that also is half in debt?"