how do I clear out code 20-amount blank? it keeps reverting $0

You can clear the code 20 by following these steps.

Log into TurboTax

1. Select tab Federal Taxes /
2. Wages and Income /
3. Scroll down to Less Common Income section.
4. Choose Miscellaneous Income.  
5. Select the very first option at the top "Other income not already reported on a Form W-2 or Form 1099".
6. Delete the record

See the TurboTax post How to file taxes with 1042-S (income code 20, resident alien) 

By @LinaJ2018