P6 R8.2 Float changing when schedule is imported

One of our PM's sent me an XER of his schedule. After I import it, the float on the critical path was zero. As soon as I schedule on my computer it goes to -20. I had him make sure he had scheduled it before he sent it to me, and he verified he has zero days of float on the critical path. His calendars came in with the schedule.

Any ideas what might be going on?

Rob