After deciphering what you are trying to explain
there should be adjustment on the float arm at the water inlet end or if an upside down cup type float cut off there should be a long threaded rod at the side of the syphone housing that raises and lowerer the positon of the float. higher the cup float is the less it fills up. if it a plastic ball float on an arm at the water inlet end is a threaded rod with lock nut release the lock nut and turn the small threaded rod so it goes closes the the valv pin sticking out of the inlet valve this will shut the water off sooner. trial and error how far out you need it. Turn the rod out test if need more keep turning until it is correct water level. Alternate is the inlet valve washer needs changing if none of this works.
bb, December 2011
