Sadly journalism these days means more often to copy press-releases and exaggerate dumb statements, then to dive into a subject and getting to the bottom of it.
In this case 1% of 7-8 billion are roughly ~ 70-80 million people, which holds 50% of global wealth is really not that hard to believe, then the reported 85/7*10^9 ~ 1/10^8 = 0.000001%!
But on a second look, i think it's more an error of the choosen title of the OP. I couldn't find his/hers statement in the BBW-article.
"The poorest half of the world’s population—that’s 3.5 billion people—control as much wealth as the richest 85 individuals."
and:
"The world’s richest 1 percent control nearly 50 percent of global wealth."
Right? Those are not the same thing.