This is a short clip explaining quantum numbers, hope it helps!!
This is because when n=2, l=1 it's a p orbital and we know that p orbitals can hold 6 electrons
It's 2 electrons b/c the numbers are describing each orbitals and each orbitals can hold 2 electrons
When n = 2, it holds s + p orbitals
s can hold (2) and p can hold (6) = 8
It's also 2 b/c the numbers are describing an orbital
Each orbital holds 2 electrons
Remember that ml is asking for the specific orbital in subshell