If you are using the recovery rebate credit to get the first or second stimulus payments then the amount on line 30 is the stimulus money and will be a part of the total refund you are seeing on line 35a.
However----you mentioned being concerned about back child support. If you owe child support your refund can be seized for the child support, including the amount from line 30. Your 2020 refund is subject to being offset if you owe child support.
When those stimulus payments were sent out in 2020, the first one could be taken for child support. The second one could not be taken---IF it was sent by itself in late 2020 or early 2021 to you. But if you are getting it as a credit on your tax return, then the rule is different---it can all be used to pay child support if you owe that much.
TurboTax never knows if you owe child support or if the IRS is going to offset your refund. If the IRS takes your refund they will send you a letter after it happens.
https://www.irs.gov/uac/tax-refund-offsets-pay-unpaid-debts
https://ttlc.intuit.com/community/refunds/help/what-is-a-refund-offset/00/26301
Reduced Refund https://www.irs.gov/taxtopics/tc203
NOTE: You can contact the IRS Treasury Offset Program Call Center at 1-800-304-3107 to ask if they have an offset for you on file. TurboTax would not have that information.
https://turbotax.intuit.com/tax-tips/tax-payments/who-can-garnish-an-income-tax-refund/L7cPPzDyc
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
