Here's how it works when you work in a different state from where you live.....and both states have an income tax (and there is no reciprocal tax agreement between the states).

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AFTER your Federal tax return is entirely filled out with every scrap of income entered, along with all your Deductions & Credits.

1) ....you must then first prepare your GA non-resident tax return.  GA will tax all of your work income performed in GA.  They may use your total income from everywhere to calculate the % tax assessed, but in the end, they only tax your GA income.   It is unlikely that you will get all your GA withholding back unless you have real low total income.

2).... then you prepare your SC tax return.  SC calculates a state tax on everything you earned from everywhere.....but then, in order to prevent double taxation, SC will allow you to take a credit for the taxes that GA "kept"  (which is why the GA nonresident tax return has to be done first).  There are questions in the software SC interview that cover Credit for Taxes paid to another state.

There's some mathematical handwaving if the SC tax rate is lower, but the software knows about it...i.e. if GA is taxing at 5% and SC at 3%, then SC only allows a credit up-to the 3% that SC would have charged.....but I haven't checked the two state rates, and it will depend on what your total income is for the year.