Holley 4160...secondary gasket blocking hole on main bodys

Holley 4160 750fm/vac secondaries w/metering plate
List # 80508-1

Pulling apart my holley 4160 carb on the secondary side and I noticed that the holley gasket was actually blocking off an open hole on the carb's main body.

Can anyone tell me what the purpose of this hole is and if it should be blocked or not?