There's only stereo samples in the "silver" version of the Heavy Hitter series.
What is meant by "3 unique drum kits sampled", is that 3 real drum kits were mic'ed up and sampled.
There's 3 folders with stereo loops in them, called Kit 1, Kit 2 and Kit 3. It's not 3 Impact kits.
The "Platinum" version of this product separately lists "3 Impact Kits" specifically (and several other additional features the silver version doesn't have).