Working on my 1040 and entering the K-1 info--as 50% owner. Box 20, reads"Z" STMT. No dollar amt. The STMT is for ded. expenses. What goes in the box? 50% of exp.?

I have the statement with a dollar amount, but no dollar amount in the actual box.   The statement is a list of deductible expenses with a total.   When I google the following---

Line 20 Z – Section 199A Information

I find it says that the amounts reported in Box 20, Code Z is the information needed by a partner/taxpayer to claim the Qualified Business Income Deduction.

I don't understand how a total of bus expenses plays into the calculations of getting a QBID, because when I read more about it, the figure in Box 20, under Z, seems to be related to income and not expenses. If you or anyone could explain this to me, I'd appreciate it.