Odds for a 0–99 draw
There are 100 possible results, so each number has a 1 in 100 chance (1.00%) of being picked on any single draw. Each draw is independent: getting 99 once doesn't make it more or less likely next time.
Pick several numbers at once
Change "How many numbers" to generate a list. Untick "allow duplicates" to get unique numbers, up to all 100 in a random order.