Live in NJ, worked in NY - treatment of unemployment comp question

Hi,

My son is a resident of NJ, worked in NY.

In 2020, had 3 months income from working at job in NY and then 9 months of NY unemployment comp.

I prepared NY nonresident income taxes, NY unemployment compensation is taxable, don't like that, but understand, calculation straightforward.

Now, on to NJ resident return, credit for income taxes paid to NY is supposed to be: NY income taxes to not include income from NY unemployment comp or taxes on NY unemployment comp. 

So - question is - how do you calculate NY income taxes to not include NY unemployment comp and taxes on NY unemployment comp?

Thank you in advance.