Hi :
I don't know if this will help you or not, but number that I entered for "Z" was the rental income (loss), the same as in box 2 of the K1. I thought that was it, but every time I tried to finish and submit my return electronically, TT did its "one last check before you submit" and wouldn't let me continue. It said that I couldn't submit electronically and to submit by mail. That made no sense. I finally figured out that it wasn't looking for that number (box 2 of the K1) but the gross rental real estate income which I found on the K3 Part II, line 3A. Don't ask me why but as soon as I went back and put that number in, everything worked.
Good Luck!
