Hi Roy,
Your carb is probably the original for your EW: AMAC made a carburettor especially for the EW - see attached.
Through the early 1920s AMAC used a submerged main jet with a row of "sprayer nozzles" along a ridge under the slide. The EW AMAC is a variant, also with a submerged jet but with a mesh under the slide instead of the row of sprayers. Not sure how well it worked. The EW is more often seen fitted with a B&B, but I'm not sure if this is because the b&B is "better" than the AMAC.
Anyway, because the main jet is submerged its length is unimportant because it lives in a lake of petrol. The jet just meters the petrol, rather than spray it as occurs in later carbs like the AMAL. Unlike later carbs, the fuel level as set by the float is higher than the top of the jet.
Cheers
Leon