All of the information arcange is using is transposed from the steem blockchain which is a public ledger IE anyone can access it. Interms of how he is computing the information he is likely using homespun( because he is a programmer) methods of analysing the data. If you would like to look at the raw values of steem some of it can be viewed on https://steemd.com/ alternatively if you having coding experience you can take a look at the different APIs that our community has developed https://www.steem.center/index.php?title=API_Libraries