monoid[a,b,c, MonomialSize => n]
The MonomialSize option specifies the minimum number of bits to be used for storing each exponent in a monomial. The exponents are stored as signed binary numbers, so n bits allows an exponent as large as $2^{n-1}-1$. Useful values are 8, 16, and 32.
The source of this document is in Macaulay2Doc/functions/monoid-doc.m2:563:0.