XP is a value that can be tracked by counters, dice, cards, or any method that clearly displays the specific value of XP that is currently on a Player.
§ 729.1.a Core Rules PDF (officieel)
§ 729 XP is a resource that is accrued, spent, or otherwise modified by Players through the course of play.
§ 729.1 The amount of XP that a player has should be marked clearly.
