How many are a “Congregation?”

Mishnah Sanhedrin 1:6
The Evil Congregation

“The Eternal speaks
to Moses and to Aaron, saying,
‘How much longer
shall this evil congregation
murmer against Me?’”
(Numbers 14:27)

Whence do we learn that ten individuals constitute a “congregation?”  From God’s excoriation of the scouts:  Altogether they were a group of twelve, but the “evil congregation” excludes Caleb and Joshua, hence ten!