PB Missions (Metal Gear Solid 5: The Phantom Pain)

Why, when completing PB tasks, for each victory they add both victory and defeat to me? I started the PB task 6 times, successfully 5 times, failed 1 time (unknowingly pressed cancel) and my win / lose ratio counter shows 5/6. There was not a single message that someone else attacked my base (if they should come at all (I xs)).