I read the two first Silo books (Wool and Origins) and at this point, I may have missed some explanations because I didn't understantd all hints.

At some point, Donald realizes Silos probably won't survive this Experiment, even the Silo number One.
I remember they talked about a Silo ranking, like a list. Do we have to understand that only one Silo will survive ? The best humans winning this competition will have the right to go out and rebuilt humanity ?

_I haven't read the last one (Dust) so please, do not spoil it._