Just forgot to mention in the last update that you need to add this to your levels.yml to let the new upgrade work correctly:
Code (YAML):
# Spawn amount
# Set how many mobs attempt to spawn in each period.
# The period can be configured in the config file.
period_amount:
1:
value
: 2
cost
: 0
2:
value
: 4
cost
: 5000.0
3:
value
: 5
cost
: 8000.0
4:
value
: 7
cost
: 1000.0
Also you can add more levels incremental yourself.