Late Sub

[foureyesallbad]

I'm white hat in a 9th grade NFHS game. I blow the RFP while A is in their huddle. A breaks their huddle and as they are approaching the line, A's coach sends in a sub who joins his team inside the numbers. The player he subs for gets to A's sideline before the snap. No delay of game as A gets the ball sapped in time. However, B's coach is going nuts because we "allowed them to sub too late for us to counter their sub!"

After the game, he insists that subs have to be at the numbers or inside them when the ready blows that way be has a chance to sub. I can't find it anywhere. Did I just blow it?

Thanks.
4eyes