iRule::ology - Table Based Rate Limiting

another question would be; why do we even bother with the "%15" ? Isn't it possible just to do something like this :

when HTTP_REQUEST { 
	if { [ table lookup "request_limit_reached" ] < 30 } { 
		table incr "request_limit_reached" 
		table timeout "request_limit_reached" 1 
		table lifetime "request_limit_reached" 1 
	} else {
		HTTP::respond 500 
	} 
}

The only benefit I see of the modulo, is that it prevents the hole code from executing each time a request comes. And hence the irule would be, I suppose, a bit faster. am I wrong ? am I missing something ?

many thanks ,

karim