Note: Carters and at least some Autolite/Motorcraft and Holley 4010-4011 have a slightly more complicated low speed system.
These have two fuel restrictions and second air bleed of sorts. Low Speed Jet: The first jet picks up solid fuel taken from the bottom of the mainwell. Economizer: This is the second jet, and restricts between the bypass air bleed and the idle air bleed.
expand the snip from Tuner and the links for how those works racingfuelsystems-Operational theory of the Carter idle restricions & air bleeds