Can someone please explain the 593 form to me?

I am new to the real estate world. I am young and this is the first time ever going through a sale of property. (It’s my boyfriends, I just do all the paperwork). I need to fill out this form but only have small pieces of information. What exactly am I withholding? How do I complete the form? I was given it yesterday evening and it needs to be in by today so the house could close tomorrow; I have tried asking the escrow company and they were not helpful. Just telling me I needed to let them know if we were withholding and how much. Please help!