code explanation

[hai061898]

First of all, thank you for sharing this code source. But there are some things I don't understand, I hope you can explain

1. What does the variable max_quantity in the file ability_upgrade.gd mean?
2. I don't really understand this part
   " func on_ability_upgrade_added(upgrade: AbilityUpgrade, current_upgrades: Dictionary):
   if not upgrade: return
   if upgrade.id == "axe_count":
   axe_count = current_upgrades.axe_count.quantity + 1
   "