OK, I think I get it now. The TT webpage states at the top in bold letters to use line 54 to enter the following fields, but then when you get down to the col.F info, it's asking for info not necessarily on line 54, but doesn't really explain that, and so that's where the confusion begins. You're still on the page that clearly states to get the info from line 54, but no, that's not the case any more... now you're supposed to do what's shown in parentheses, getting the sum of values from other lines, and then subtracting that from the actual value on line 54 col.F.
