If you are under the New Jersey filing threshold, Lines 30 through 49 of your New Jersey Form NJ-1040 should not be completed.
New Jersey instructions for Form NJ-1040 State of New Jersey Income Tax-Resident Return, page 23:
Line 29 - New Jersey Gross Income
Subtract Line 28c from Line 27 and enter the result on Line 29. If less than zero, make no entry.
Not Required to File a Return
If your income for the entire year is not more than $20,000 ($10,000 if your filing status is single or married/CU partner filing separate return), you have no tax liability to New Jersey and are not required to file a return.
Even if you have no tax liability, you need to file to claim a refund if you:
Do not complete Lines 30 through 49. Continue completing the return with Line 50. (See instructions on page 37.)