How to understand and report my w-2 state income

I live in NJ and work in PA and I have a 2-page w-2. Page one has the Federal reference and filing copies and the NJ reference and filing copies. Page two has the NJ reference and filing copies and city/local reference and filing copies. The NJ info on page 1 is different than the NJ info on page 2. On page 1, box 15 says  NJ and boxes 16 and 17 are filled in. On page 2, box 15 says NJ and box 16 is the only one filled in. Both box 16 amounts are different, but they add up to box 1. However, box 16 on page 2 is the same number as box 18 on my city/local copy, which only has boxes 18-20 filled in.

 

My question is, when I'm doing my NJ tax return, do I add both box 16 amounts together to report as income? Also, since there is no PA copy, do I file a PA return? If I do, am I supposed to use box 18 on my city/local copy as my PA wages because box 16 is blank?