Clarify behavior of Channel.Supply.
Clarify behavior of Channel.Supply.

Thanks to jnthn for clarification.

dha/doc,tbrowder/doc,MadcapJake/doc,MadcapJake/doc,MasterDuke17/doc,jonathanstowe/doc,dmaestro/doc,jonathanstowe/doc,stmuk/doc,perl6/doc,jonathanstowe/doc,stmuk/doc,stmuk/doc,perl6/doc,antquinonez/doc,jonathanstowe/doc,gfldex/doc,gfldex/doc,antquinonez/doc,antquinonez/doc,dmaestro/doc,gfldex/doc,gfldex/doc,perl6/doc,dha/doc,MasterDuke17/doc,dha/doc,dha/doc,MadcapJake/doc,MasterDuke17/doc,dmaestro/doc,tbrowder/doc,stmuk/doc,stmuk/doc,antquinonez/doc,antquinonez/doc,MasterDuke17/doc,MadcapJake/doc,MadcapJake/doc,dha/doc,tbrowder/doc,perl6/doc,jonathanstowe/doc,dmaestro/doc,dmaestro/doc,gfldex/doc,tbrowder/doc,perl6/doc