PZ19 Carburetor question

[nickaloadien]

I have this new PZ19 Carburetor and wondering if anyone knows what this bottom bowl hose connector and little hole is for on top? Maybe I am supposed to connect a gas line from bottom to top? Fuel seems to pour out of the top hole when I tilt the carb upside down. Also anyone know best way to tune this carb? I’ll supply photos

 

[noah9988]

Bottom hole is the bowl drain, top hole is the overflow.