It's pretty simple.
For basic commutators, there are two digits. [X, Y]. For example, [1,1]. This means that X is 1 move, and Y is 1 move.
The way this is executed is X, Y, X', Y'.
So, say X = R, and Y = F...
A [1,1] would be R, F, R', F'.
Like I said, pretty simple.
Then there are conjugates. A conjugate looks like this: [1:1]
This is performed X, Y, X'.
You can combine the two, for example [1:[1,1]]
That would be X, N, M, N', M', X'.