The 600 million is just the maximum amount of coints that have ever existed in the coins history. Total supply is the amount of coins that exist right now. Total supply takes account of the burned coins.
Circulating Supply is the best approximation of the number of coins that are circulating in the market and in the general public's hands.
Total Supply is the total amount of coins in existence right now (minus any coins that have been verifiably burned).
Max Supply the best approximation of the maximum amount of coins that will ever exist in the lifetime of the cryptocurrency.
https://coinmarketcap.com/faq/