"There are ten toes in this woman's feet."
Translation:इस औरत के पैरों में दस उँगलियाँ हैं।
अंगूठा is the big digit on either your foot or your hand, i.e. your thumb or your big toe. If it's not clear from context, you precede it with "पैर का" or "हाथ का" to disambiguate.
उंगली is any of the digits on either your hand or your foot. I.e. a finger, the thumb, or a toe of any size.
I had the same thought process and gave the same wrong answer.
After thinking it through, I think I see their point. The term "पैर के उंगलियाँ" literally translates to "foot's fingers". Since we're saying "on this woman's feet", we don't need to disambiguate between "foot fingers" and "hand fingers". Saying "foot's fingers" is redundant.