GameStop Corp on Monday increased the value of new stock it may sell from $100m to $1bn, as the United States video game retailer seeks to capitalise on a surge in its shares from a Reddit-driven rally this year. GameStop stock has rampaged over 900 percent higher since January in highly volatile trading as amateur investors organised on social media sites such as Reddit staged a stubborn buying spree, winning out over Wall Street hedge funds that had bet against its shares rising GameStop’s shares fell as much as 13.9 percent on Monday. They briefly reversed course to trade up slightly, but were trading lower again at 11:53 am EDT (15:53 GMT) at $188.50.