Liquidity is not same as trading volumn. HiBTC trading volume are high at many market, but not highest. There are many higher reported trading volume exchange there. Liquidity number is supposed to be real number
after removing scamming trades. Liquidity most likely is real number on bids/asks and traders can obtain those in real trades.
bids/asks could be wash trades too with self trading money. But it is unknown how much wash trades there in HitBTC. But HiBTC usually has very tight bid/ask spread so that my impression is that liquidity at HitBTC was real on dogecoin, litecoin, bitcoin and ethereum markets. I only trades those there and do not know other market that much. But my impression of past experience says that HitBTC liquidity ranking number 1 is reasonable and believable.
I can only assume liquidity is based on CMC counting all the buys and sells in each order book or republishing what they're told by the exchange. Both can be easily faked if they can be bothered.
If you can find anything about how CMC measure it then let us know.