Melmi

Base 1 usually uses ones, because it represents summation at that point. Using zero as the numeral would be a bit awkward. Also historically zero is pretty new.

Tally marks are essentially a base 1 system.

Funny enough, there’s a point in a later book in the series where they suggest the “ultimate question’” that 42 is an answer to could be “What do you get if you multiply six by nine?”