You know that every user can transfer BTS from one account to another acount.
This excel file which account is getting bigger and wich one is getting smaller.

For example September 2017

That numbers tell us china exchange wallet get smaller,this wallet send their BTS to other accounts.

chbts -> total received BTS - total send BTS = -146.963.731 BTS (This account has 146 M less BTS in this month)

When you sort September 2017 column descending then you will see who is bigger BTS receiver

bittrex-deposit -> total received BTS - total send BTS = 163.761.731 BTS (This account has 163 M more BTS in this month)