You can charge a battery at less than 1C, but also many can be charged at higher than 1C (I have some 3C batteries). But correct 1C is 2.8 amps for a 2800mah battery. You can charge larger than 6000 mah batteries, it just will take longer.
Ideally you want to charge lipos at a minimum of 1C.
And welcome to the electric part of the hobby.