Vasidodekaphobia is the fear of duodecimal, or dozenal.
Average people count like this: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; but however, Donald P. Goodman shown above counts like this: 1, 2, 3, 4, 5, 6, 7, 8, 9, X, E, 10
Dozenal is just base 12, or the symbols 0123456789 with two added symbols, X (dek) and E (el). 10 is 12 in decimal, pronounced "do." 100 is 144 in decimal, pronounced "gro." 1000 is 1728 in decimal, pronounced "mo."
People might have this fear because of tradition or the two extra symbols.