That can change from year-to-year.
KS only allows you to subtract the SS amount that the Federal 1040 form actually taxed. So if line 6b on the Federal 1040 is zero (or empty), there is nothing to subtract since line 1 of your KS K-40 didn't include any SS in the first place.
IF you haven't finished entering all your 2020 income in the Federal area yet , that could change. Some tax forms haven't been issued yet...my Brokerage isn't sending mine out until after 13 Feb.
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Note too: Line 2 of the KS-40 can include other subtractions or additions from their Schedule S...so the value on line 2 may not be the exact value of SS that was Fed taxed from line 6b of the Federal form 1040. For the details on that type of situation, you would need to refer to your KS Schedule S, to see how line 2 of the K-40 was calculated.