Cutting discs generally are not directional i.e. you can put them on either way. If they were directional there would be an arrow on the label to indicate which way they should rotate. On this basis it doesn't matter which way they are mounted, label in/label out. The label is only there to provide information eg. barcode, size, use etc.
Grinding disks are generally dished and can only be installed one way around or they will interfere with the guard.
Just an aside. (In my opinion) Angle grinders should always be used 2 handed (for safety) clamp the job down correctly and you lessen the risk of damage to yourself.
