Unlike the real treaty, which was by tonnage not number, the game doesn't have a hard limit. Instead it is based on Production Cost. The Base is the UK (unless for some reason they left the treaty, then I think it goes to the US).
Also unlike the real treaties, it doesn't split them by type (Carriers, Battleships/Battlecruisers, Cruisers (two categories)), but instead just lumps them all together (except the Light (Category B) Cruisers).
Again, unlike the real treaties, there is no ratio, so instead of the 5:5:3:1.75:1.75 all signatories just have to avoid going above (or at least not very far above) the leaders total.
Most games, the US will not be able to finish the 2 carriers and 3 heavy cruisers in their starting que without going above the limit and getting an ultimatum from the UK and/or France. This might have changed now that the AI actually keeps working on the ships in the UK starting que, but I haven't tested it recently.