The Ironsworn character sheets have bubbles for tracking the experience that you mark by fulfilling your vows. The portrait character sheet has 30 bubbles, and the more-recently-released landscape sheet has 50 bubbles. Chapter 2 of the rulebook explains how to use them, with a key note that "to start, your experience is unmarked", and instructions to "Mark an ‘X’ on your character sheet for each point you’ve earned" and "Replace the ‘X’ for each point spent with a filled-in dot."
You can spend experience points to add a new asset or upgrade an asset when you focus on your skills, receive training, find inspiration, earn a reward, or gain a companion (per the Advance move). Is there a practical cap on the number of experience points you can have (beyond the character sheet you choose and the assets you buy)? Should you clear points put toward an asset or leave them filled in?