NJ gives you the higher of a property tax deduction OR the $50 property tax credit. There are special calculations if you claim credit for taxes paid to another jurisdiction. See Schedule NJ-COJ and Worksheets H and I ("eye") in this instruction booklet:
Instructions for the 2020 NJ-1040 (state.nj.us)
Also note that you could end up switching back and forth between the deduction and credit from year to year, depending upon that year's particular tax situation.
