Form 8096 line 4a and 4b

I had passive income of $13000 for rentals, and a loss of -9000 in businessMy MAGI is above the threshold so I have to pay the NIIT.

 

TT fills in Form 8960 automatically with 

4a as 13000

4b as 9000

c Combine lines 4a and 4b = 22000

 

Then I am taxed 3.8% on 22000

 

BUT 9000 was the loss, not income, why does it not get added as an adjustment as negative, instead gets added as a positive and increases my tax. It is negative in the worksheet. 

 

Thanks!