I quoted that same line in another comment...

They don't monitor the entire network, they only count the peers that are currently connected to their nodes.
> Notes: Data updated every 2 hours. Data based on actual reported peers to our Bitcoin nodes. 

Filiprogrammer

BitMex's tracker is obviously immature; they report below 500 nodes, while CoinDance reports over 23k.

I like that they publish their view for transparency, although anyone interested in this information must realise that obtaining an objective view of the entire network is practically impossible.

bitcoin

Bitcoin node client tracker - BitMex Research

Scoresby

BitMex's tracker is obviously immature; they report below 500 nodes, while CoinDance reports over 23k.

I like that they publish their view for transparency, although anyone interested in this information must realise that obtaining an objective view of the entire network is practically impossible.