That box is not looking for a number, but rather a "QBI Component worksheet" to which to link. Delete anything (including any spaces) you have in that box, and then "double-click" on the empty box. You should see a QBI Component worksheet for your Schedule C or Schedule E worksheet in the list of options. If so, link to that QBI Component worksheet.
TurboTax somehow "believes" you have previously disallowed QBI losses. Check the section at Federal>>Income>>Other Business Situations>>Net Operating Loss/QBI Carryforward Loss to look for any entries related to a QBI Carryforward Loss.
This is a new thing in 2019, because the QBI deduction just started in 2018. Now, for the first time, QBI losses from the previous year (2018) are being used to offset QBI income in the current tax year (2019).
If you had disallowed QBI from 2018, that needs to be carried to your 2019 tax return. That 2018 disallowed QBI loss should be on some sort of carryover worksheet from your 2018 return. If you used TurboTax in 2018, it will be on the 2018 Federal Carryover Worksheet, in a section entitled "Qualified Business Income Deduction (Section 199A) Carryovers".
As background, when you have a business that qualifies for the Qualified Business Income (QBI) deduction, your deduction is based on the income of the "QBI business". No QBI business income, no deduction. And, if you have a loss on your QBI business, that loss gets tracked and "carried forward" to be offset against next year's QBI business income when calculating that next year's QBI deduction.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
