The facility must have a minimum of two physical barriers which stop the GM animals to be held from escaping and stop animals of the same species, or of any species able to interbreed with them, from getting in; the guideline gives two fences, or a building plus a fence, as examples. Where the primary barrier is a building (a shed or barn, for example) it must be enclosed fully, and a secondary barrier must surround every way into and out of it. Where fencing alone is to stop escape, the perimeter must have a minimum of two full rows of fence.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.