Yeah, I just looked at like Gloomhaven and they just have one spot that you erase and write in the updated gold amount. That seems fragile over time to me.
Now if this was a real product I offered. I would probably just have 12 Knowstone tokens. And the max capacity you can "hold" at any given time are those 12. So if you go over that amount after a run, would have to upgrade some things immediately to avoid wasting excess. But, since this is a PnP it made sense to track lifetime gains, but that would save a ton of space just tracking current value of Knowstones.