Yup, you're right - this is a real mud hole. But anyway the point I was trying to make was that the first number relates to the (approximate) bullet diameter, and the second to the standard charge of black powder.
The .38-40 cartridge (a.k.a. .38WCF) originated with Winchester in 1880, and was first chambered into their model 1873 rifle. Colt started to use it their Single Action Army in 1884, which was the same year they came up with the pump-action "Lightning" rifle and induced the cartridge makers to create the .32 CLMR, .38 CLMR and .44 CLMR. "CLMR" stood for "Colt Lightning Magazine Rifle," and all were interchangeable with their Winchester counterparts (.32-20, .38-40 and .44-40). The reason for all of this was that Colt didn't want to mark anything on their guns that might contain the slightest reference to Winchester. So the cartridges weren’t really different, just the names.
Clear as mud?? Well I said it was a .....