new installed Fluidmaster Toilet Tank Fill Valve, found that

[savetime]

Occasionally， there is a leaking happened , not much, but some water leak to Bowl, just a moment and then stop.
why so and how to fix?
Thanks

 

[breplum]

flapper can leak, so , use either the special tablets in the tank for revealing leaking flapper, or food coloring.
If your tube into the overflow is not held above the top of the tube then, that is a problem and needs a clip to keep it above the overflow tube.

 

[havasu]

A pic of your toilet tank will reveal the issue usually.