if they're all individual (as in physics/chem/bio gcses as separate qualifications), you learn all the higher tier/"chemistry/physics/biology only" chapters and your exams are 1h45m, then triple
but i do 2 papers for each science and i was told i do triple
Triple and double science students both do 6 exams. It's just that they get different papers, since triple cover slightly more content than double students. This is also why triple students get an additional 30 minutes to complete their exam. Single science students do 3 papers. Hope that clarifies anything.
Also, combined, trilogy, and double are all the same thing.