First of all, where's the short rubber or plastic tube from the valve
body to the overflow drain tube?

Second, the screw on the valve end of the float lever is probably the
adjustment; turn it IN a 1/4 turn and see if that solves the problem.

Otherwise, the "seal" or washer inside the inlet valve ought to be
replaced. $2 +/- at local hardware.
Turn the water OFF.
Remove the little locking tang from valve body, twist the top of the
valve OFF. The rubber seal is before you.

Good pictures!