Deductions & credits

When filing NY resident tax form, in the "Taxes Paid to Another State", there is a field under section "Income Taxed by New Jersey", that is, "Portion Taxed by New Jersey".  What should be entered for "Amount if different"?

 

In my case, I see all wages amount is under "Portion Taxed by New Jersey". Should I just leave "Amount if different" blank? Thanks.