there’s a 0 on the die

to roll 1:
1st, 0 x 10 = 0
2nd, 0+0 = 0
add 1, 0 + 1 = 1

to roll 100:
1st, 9 x 10 = 90
2nd, 90 + 9 = 99
add 1, 99 + 1 = 100