How to interpret lifetime score I can not understand what the following numbers mean:


  Gligorić had the following record against the world champions he
  played against: Max Euwe +2 -0 =5, Mikhail Botvinnik +2 −2 =6, Vasily
  Smyslov +6 −8 =28, Tigran Petrosian +8 −11 =19, Mikhail Tal +2 −10
  =22, Boris Spassky +0 −6 =16, Bobby Fischer +4 −7 =8, Anatoly Karpov +0 −4 =6 and Garry Kasparov +0 −3 =0.


I took them from here. I do understand that it tracks statistics against a particular opponent in all games, but what is this strange mathematics mean: +8 −11 =19?
+8 -11 =19 means: Won 8, lost 11 and drew 19