Form 4952 line 1 and line 5 and line 8

I received K1 form, the number in box 13H is $2127, and in box 20B is $20812. I entered 2127 in TT in "Investment Interest Expense" and 20812 in "Investment Expense". Now, my form 4952 is showing:

Line 1: 3742

Line 3: 3742

Line 5: 20812

Line 8: 3742

 

My first question is why line 1 is showing 3742? Where does the number 3742 come from? The second question is why line 8 does not allow me to deduct the total expense 22939 (2127+20812)?

Thank you for your help.