If the Fluidmaster fill valve has a stainless steel rod and clip, adjust the water level by pinching the clip and sliding it up or down the rod to raise or lower the water level. For the newer style valve with the plastic adjustment rod, turn the screw at the top of the rod to adjust the water level. Flush the toilet to lower the level and turn the screw, using a screwdriver or your fingers to adjust the float.
Toilets have a mark inside the tank indicating the proper height for the water. If you cannot find the mark, the water level should be slightly below the overflow tube. Continue adjusting the level until the toilet reaches the level and the valve shuts off the water.
Sometimes, it is not possible to adjust the level to the proper height using the adjustment rod alone. In such instances, adjustment requires raising or lowering the height of the fill valve. Turn off the water supply to the toilet and flush the tank. Grab the shaft of the valve under the float so you hold it up in position. Remove the top cap by twisting it counterclockwise and disconnect the refill hose from the valve. Turn the valve until it clicks to adjust it, and replace the hose and cap when finished.