It means your engine isn't getting enough gas and its running lean. Make sure all the jets are clean, they may need to be blown out with air. If that carburetor has a main jet adjusting screw it needs to be opened. My garden tractor and an old Toro Grass King mower have that feature on their carburetors for enriching the fuel mixture.
Check your float to make sure it's set high enough for your fuel level. Hal