I think this is a mistake. They already issued one correction from "20-member" to "20,000-member". The author seems to have serious problems with numbers. Look at the first paragraph:

> Facebook Inc took down a popular Wall Street discussion group, Robinhood Stock Traders, in a move that its founder on Thursday described as backlash for conversations buoying shares of GameStop Corp and other companies this week.

First, a typo, "buoying". But it also says "this week". So what they meant is probably Jan. 27.