Calculate your full income according to these date ranges. The form will not duplicate your income. It is done this way to verify that income was earned unevenly throughout the year.
For more information, see: 2020 Instructions for Form 2210, page 9, Schedule AI—Annualized Income Installment Method.
For more information, see: How do I add Form 2210?
However, if you are experiencing difficulty, please see to sign up for updates: Why is my Form 2210 not calculating lines 18-26 correctly?