From "Journey to Babel":
CHEKOV: Fire control locked into the computers, Captain.
KIRK: On my order, fire photon torpedoes two, four and six.
Widest possible scatter.
CHEKOV: Aye, sir.
CHEKOV: Full spread missed, sir. They're moving too fast for us.
Six photon torpedo tubes for that little area looks like quite a lot and too much, doesn't it?