TTC bus brown line rule

I have use express ttc bus and I have seen too much people in bus. I gave up my coins in box. The driver said again again you should be under the brown line and I look the people, people jammed in bus but bus front side is empty. I jammed with this people and bus moving. After a people went to front side of bus. The driver stop the bus and again said same thing. "You should be under the brown line". That's bullshit because the bus has space but we don't use this space.