Dude, the polemic is showing. He is not confused, he just has to check WHO supplies the troops. And it was obvious what he meant. Pls don't be that guy...
The supply limit depends on the party supplying the unit, as supply is also calculated from the fictive "supply stock pile" in the homeland, IIRC. And other stuff factors in as well (local production, infrastructure, overflow ect). That means for example that a German player might see a different supply level in a province than a russian player in the SAME province.
The only thing confusing me a bit would be: what if all transport routes to Japan are cut, but since Spain supplies Japanese volunteers, they are still in supply. Do those troops still get equipment? But since the devs said (IIRC) that equipment has to be transported (so its "flowing"), it can be sunk. thereby Japan would have to ensure a safe route to Spain in order to re-equip its volunteers there