What is meant is n tickets are sold, and then you do something like 'each ticket bought a particular plutonium atom out of n atoms; whichever atom decays first is a winning ticket'. Many Worlds says that each atom decays first in some world-line.

The idea is to, like the least convenient possible world, to avoid a cheap rhetorical escape like 'I deny the trilemma because in my world the possibility of winning has already been foreclosed by my buying a predetermined losing ticket! Hah!'