Population size is always 40, sample size is the number of cards you see by turn N (6+N on the play, 7+N on the draw), successes in population is # of lands in deck (15-19), and successes in sample is just N
In any case, its a very powerful ability
Note that this destroys any permanent, so if you need to get rid of that Gaeas Cradle your opponent has been abusing, Alpha Deathclaw has your back
It currently sits at roughly $3
But here is this set we can kick Dismantling Blow for two cards, kick Orim's Thunder to burn down a creature, Aura Mutation for some 1/1 Saprolings, drawing a card off Aura Blast, and many more effects in just one Block
Of note is Boco the Chocobo, who you automatically get early on in Chapter 2, who quickly produces Black Chocobos, which are flying Glass Cannons, and Red Chocobos, which are mobile Lightning Bruisers