Araye is correct on this one. Most 10 sided dies in the 80s and up started with 0 and ended with 9, so did the 20 sided dies... so that a 100 was actually two rolls of 0 on a d20. However, the four, six and eight sided dies went 1-4, 1-6, 1-8. This was because you could use the 10 sided multiple times to generate numbers going up to 10, 100, 1000, et cetera if you did not have the cool l33t d20 which was relatively new back then...