Yes, but as I read they not burning the 85% of the total supply, they burning the sold tokens.
Example:
I buy 1 million token exactly, then few days later I sell, so 85% from 1 million (850 000) will be burning from the real total supply. Maybe I did not understood it well!
It's still easy.
They create 1 billion tokens, sell 500 millions of them and keep the other 500 million tokens in their own wallet.
Now they should sell 85% of 500 million tokens which is 425 million tokens. They burn 425 million tokens from the 500 million tokens they have kept in their own wallet.