What am I doing wrong?

im trying to measure my bra size bc I need to buy more and the ones I wear rn dont fit the best

Im using the VS app and it tells me to measure the band size and bust size with a soft measuring tape

I measure 33 for bust size and for band size 26 but the app keeps telling me it can't calculate a size with those inputs and to double check my measurements even tho theyre correct?
What am I doing wrong?
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