Tuition transfer from dependent max is $5000. We've done dependent's return as designated such. Why is the TTO stating that the max transfer amount is less than that?

line 9 on schedule 11 is $6239.10
student used $0 on their return and designated max transfer to parent of $5000.  Software will only let us transfer $4238?  I believe parent could use the extra credit on his schedule 13.