You can enter the exact NY amount by changing the Box 16 amount for NY to the amount your employer reported as the correct NY amount. You may also allocate by the number of days or a calculated percentage of the total amount using the allocation screens in the NY nonresident return. If it is a few dollars off, that is fine, as long as all your income is being taxed by your resident state, which we are assuming is NJ.
If your employer has your entire wages as the Box 16 amount for both NY and NJ as it appears they do from your original post, make sure that when you are doing your NJ return, you only report these wages once. You do this on the screen that says Let's Confirm Your Taxable State Wages. Remove the NY wages. The NJ wages remaining should be at least as much as the federal wages reported in Box 1, possibly more as NJ does not allow deductions for contributions to a retirement account. If you do not remove the NY wages, they will be double-counted on the NJ return.
