I've played this game three times now, but for some reason I now can't remember or find what the 🔥 markers in the mine mean. Are they a requirement like the numbers they're next to? Are they a reward? As a requirement, it's unclear how much reputation you would need. As a reward, it's weird that the icon would be placed next to a requirement indicator (the skill number). Plus, the rules only say that you collect gems or coins.
They are a reward of +1 reputation. You're looking at the advanced side of the board (presumably your earlier plays were on the basic side), and the rules for that are toward the back.