It may be, but not necessarily. Only that portion of Schedule A, line 17 that's directly connected to the production of unearned income would be entered.
The popup you're seeing refers to the portion of the amount on line 17 of your child's Schedule A (Form 1040), or line 8 of their Schedule A (Form 1040-NR), that's directly connected with the production of the unearned income that's shown on line 1 of Form 8615.
According to Directly connected in the Instructions for Form 8615:
Itemized deductions are directly connected with the production of unearned income if they are for expenses to produce or collect taxable income or to manage, conserve, or maintain property held for producing income. These expenses include custodian fees and service charges, service fees to collect taxable interest and dividends, and certain investment counsel fees.
