How are state withholding taxes calculated on federal return?

I sold my house in 2019. I paid an estimated Colorado withholding tax based on net sales price. 2 questions: 1) where do I include this expense to adjust my selling expenses? 2) since this was an estimate I expect to get a refund from CO. based on getting a $250,000 exclusion.  I won't know this amount till I file 2019 federal taxes how do I calculate?