I had 3 of these while I opened some chests. It say that it has 50% chance to get a bonus xp while crafting. Although when you discover a recipe it is 100% sure that you will get bonus xp. Does the bonus from the token stack with the original bonus from discovery? If not, since that I skill up my crafting 90% with discoveries what do you suggest to do to get the full potential of these boost tokens? How should I use them for best results?