How is total supply of token calculated?

Total supply refers to the number of coins or tokens that currently exists and are either in circulation or locked somehow. It is the sum of coins that were already mined (or issued) minus the total of coins that were burned or destroyed .

Thus after 100 billion Dogecoins are created, rewards will continue at 10k each block. This will help maintain mining and stabilise the number of coins in circulation (considering lost wallets and various other ways coins may be destroyed) at 100 billion.”

Total Supply is the total amount of coins in existence right now (minus any coins that have been verifiably burned) . Max Supply is the best approximation of the maximum amount of coins that will ever exist in the lifetime of the cryptocurrency.