AFB Carburetor Question

See attached photo showing the front of my AFB Carburetor. The two smaller screws are idle jet screws. What is the larger screw between the idle jet screws? Can’t seem to find any info on it.

View attachment 1716371950

The large screw is the By-pass idle circuit adjustment:
PXL_20250301_003113205.jpg

Adjustment:
PXL_20250301_003201541.jpg
PXL_20250301_003232719.jpg

Reference:
PXL_20250301_003240604.jpg