In order to use "Premium" you must have actived the "Regular" subcard first 🙂

Premium Subscriber: Our premium subscription cards can only be used if you are already a gold subscriber. Once activated, you will gain an extra 5x the experience rate as a gold subscriber, which will bring your total combat experience to 20x (additional experience can be gained if you train in the wilderness or are skulled in the wilderness).
In additon to the experience boosts, you will also gain the following perks as a premium subscriber:
- No global chat delay.
- Idle time increased by 10 more minutes.
- Premium subscriber rank on the forums and in-game.
- The ability to use our new stat changer.
- 1x additional wilderness experience.
- 1x additional skull boost experience.

I think it was Duke Of Lumbridge who you had to talk first to start the quest? Worth a shot 😄

Thanks for this info. What does "1x additional wilderness experience" actually mean ?

lets say experience rate for you is at 15x then u step in wilderness and one x is added so it would then be 16x 😉