Add benchmark with 17 data shards and 3 parity shards with 16MB each, and correct comments.
Add benchmark with 17 data shards and 3 parity shards with 16MB each, and correct comments.

NicolasT/reedsolomon,lukechampine/reedsolomon,fwessels/reedsolomon,somethingnew2-0/reedsolomon,klauspost/reedsolomon,beni55/reedsolomon,justmao945/reedsolomon,NicolasT/reedsolomon