How do I calculate double-taxed income on my NJ state return?

I am trying to determine the appropriate credit on my NJ return for taxes paid to other jurisdictions. For some background:

- Status is married filing jointly

- My wife and I live in NJ. I work in NJ and she works in NY

- Box 16 on her NY W2 is $150. Box 16 on her NJ W2 is $70 (using simple numbers)

- There was a period of time last year where she lived in NY, which is why I'm thinking box 16 on her NJ W2 is so low. I looked at her W2s from last year and they were nearly identical. But with her NJ wages being reported as much lower this year, its significantly impacting the credit we get for taxes paid to NY

Does it matter the number of days we lived in NJ vs. the number of days we lived in NY?

Any assistance is much appreciated.

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