I am filling two dependent children's tax returns. One of the questions in TT is "Your parent's total net investment income for all other children." What's that mean?

all other children where form 8615 was included with their return

Enter the total, if any, from Forms 8615, line 5, of all other children of the parent named above. Do not include the amount from line 5 above....................

the amount that goes on line 7 of form 8615

https://www.irs.gov/pub/irs-pdf/f8615.pdf 

Why doesn't TurboTax allows me to enter a number in Line 7 on Form 8615 (Enter the total, if any, from Forms 8615, line 5, of all other children of the parent named above). 

What a bogus reply, Turbo tax needs to hire knowledgeable people who give proper and definitive replies and not cryptic nonsenses replies.

This question remains unanswered.