Understanding Lister D float bowl drillings

Today I stripped the Lister D float bowl (early D engine brass float bowl assembly) I'm struggling to understand why it has a drilling at the bottom of the bowl as well as the normal float needle shut off. The drilling or hole (which looks like a removeable jet) is connected to the same port or drilling that feeds the needle shut off. I therefore cant see how this can work as surely the petrol will just continue filling and flooding the float bowl. What's going on here is something missing?
See photo.

Oops, I had a real blond moment there as of course the two ports or holes are not connected or at least they shouldn't be. I was blowing the holes out with an air line and it felt as if they were connected. Why didn't I think more first before posting this. Aw well possibly it had someone thinking: oops: I promise to think more next time

Oops, I had a real blond moment there as of course the two ports or holes are not connected or at least they shouldn't be. I was blowing the holes out with an air line and it felt as if they were connected. Why didn't I think more first before posting this. Aw well possibly it had someone thinking: oops: I promise to think more next time