Shares of Koss Corp KOSS.O, BlackBerry BB.N and GameStop GME.N dropped between 0.3% and 4%. By Medha Singh June 4 (Reuters) - Wall Street's main indexes were set to open higher on Friday after data showed smaller-than-expected jobs growth in May, easing concerns about the economy running too hot and causing an early tightening of monetary policy. Worries that a robust economic rebound could lead to a prolonged period of inflation and prompt the Fed to contemplate paring back its crisis level support have weighed on investors' minds recently.