(CNBC) The jaw-dropping rally in GameStop on Monday caused losses approaching $1billion for short sellers, according to data from S3 Partners. With GameStop soaring 74%, short-selling hedge funds suffered a mark-to-market loss of $838 million in the brick-and-mortar video game retailer, data firm S3 Partners said. “Expect short covering in this stock as it already had a 100/100 squeeze score prior to today’s trading,” said Ihor Dusaniwsky, S3 managing director of predictive analytics.