Then, when in the most dire circumstances, where a roll of one would be absolutely disastrous, he pulls out the prepared dice. He now has in his hand a die that has rolled two ones in a row. Pete knows the odds of a d20 rolling three ones in a row is a puny one in 8,000. He has effectively pre-rolled the ones out of the die, and can make his crucial roll with confidence. Furthermore, being scientific about it means he knows that it doesn't matter who rolls the die for the third time, so he has no qualms about sharing his primed dice with other players, if that's what it takes to avoid disaster.