New Jersey IRA Withdrawals cannot delete entry

In Section 1 - IRA Withdrawals, Part A - Taxable and Excludable Amounts, Line 4a and 4b.

Instructions indicate to complete either line 4a or 4b. Because this is the first year of withdrawal, Line 4a should apply. There is a zero in Line 4b and it cannot be deleted. Because there is a zero in both Line 4a and Line 4b and error is displayed when running a check. How do I delete the zero in Line 4b? I have tried in both the check and the form but neither work.