Adding some docs about the meanings of the soft/hard limits
Adding some docs about the meanings of the soft/hard limits

Summary: As in title.

Reviewed By: jalopezsilva, maxgeorg

Differential Revision: D8851219

fbshipit-source-id: 03a5505255b851c44713f5491af902d272a14620

facebook/wangle,facebook/wangle,facebook/wangle