That's the ranking for the exchanges with the highest volume, yes, and P2PB2B is the top of the exchanges. But you should know that bots can add up to hundreds of millions of dollars each day. That's why you are often stuck by buy and sell at exchanges like P2PB2B, Fatbtc, Bitforex ... because there are only bot trades there, very few real people. so never trust the volume at CMC, it's all a rough calculation. To find out what a really good and highly liquid exchange is, look at its community. Binance has the largest community in the crypto market and it seems to be the most buying and selling exchanges of bitcoin (and no shitcoin in there).