Bone Group SOP
The Bone Group SOP groups primitives by common bones (shared bones). For more information regarding using Bone Groups for deforming geometry, see this article: Deforming_Geometry_(Skinning). All capture weights are re-normalized.
Max Bones Per Point - Trims the number of bones per point by ignoring the bones with the lowest weight until this maximum number is met.
Max Bones Per Groups - The maximum number of bones allowed per group of primitives. If there are more bones than this number, a new group is created.