OPTIMAL – The address has sufficient amount of ETC on it, you can send a lot of transactions.
GOOD – About 6-8 transactions left.
CRITICAL – About 2-5 transactions left.
FATAL – About 1 transactions left.
ZERO – No more ETC on address, you should send ETC to this address.
Please consider the following:
Making a simple transaction on the Ethereum Classic blockchain needs much lower amount of GAS than setting up a provider account, as it involves contract calling as well. This is why the levels hugely vary in transaction count.