So _assuming_ per the Wiki that he does in fact own 15%, and that the cash portion of the deal is $2.6B ($3B - $400M), that 15% would be worth $390M in cash, and another $60M in stock.
So 390 + 60 + 550 = $1B![]()
That $550M number already includes what his ownership was in Beats (at the lower valuation of $2B). You are double counting that.