Sept 16 (Reuters) - Shares of ForgeRock Inc jumped 40% in their New York Stock Exchange debut on Thursday, giving the digital identity management company a valuation of about $2.8 billion. Shares of the company, backed by an affiliate of private equity firm KKR & Co, opened at $35, compared with their initial public offering price of $25 per share. (Reporting by Sohini Podder in Bengaluru; Editing by Shinjini Ganguli)