Wire size & current capacity
“Two cables single phase” means they’re giving the capacity for two wires pulled together through an enclosure and carrying the same current. That’s usually hot and neutral, but it could be two hots or two neutrals (though there are often other code issues there).

Why is that needed? The ampacity limit comes from the maximum acceptable temperature rise under specific conditions. These wires are used to carry current in a conduit or raceway. So that’s how they’re rated: how much current can we carry in a specific reasonable situation before the temperature rises too much. (Note that the cable tray case cools better, so can often handle more current)

The various electrical codes specify how to get from these kind of ratings to ones with more wires, mixed sizes, etc.