I understand this sounds ridiculous at first but I got asked this question by a supply teacher $3$ days ago and I haven't been able to answer it so it's driving me insane.
I got given two hints:
It's over $10$ fingers
because we have $10$ fingers we count in base $10$ which is why for us $7\times7=49$
On
7x7 = 49 in base 10. If the alien says it's 41, it's base is higher. If we try with base 12
$$ 49 / 12 = 4 \land 49 \% 12 = 1 \implies 49_{10} = 41_{12} $$
But how many hands does it has? One? two? ten? Are they evenly distributed? Let's just assume they are humanoid, so two hands, therefore six fingers per hand?
The question is equivalent to $ 7 \times 7 = 4 \times n + 1 $, and solve for $n$ (the number of fingers). Hence $n = 12$.