"Двадцять три гривні"
DL wants you to learn Ukrainian verbal numbers, so they avoid numerical numbers. I know that in this case it is English, but the DL developers probably didn't pay attention, so it asks for literally "twenty three," [20 3]. Report it. They fix reported issues faster than addressing comments. I just avoid numerals entirely in Duolingo and only write out the verbal numbers. Also, they forgot the hyphen (-) in "twenty-three," so that could be why "20 3"