I've seen it pop up on my screen a couple of times and have no idea why. There are tons of seemingly small things in this game that there are no explanations for in game, and it's starting to get a little confusing. --- GT: Adamantus
As far as I can tell from when I was playing the beta, the progress made in your squad perks gets reset to the previous amount (so if you were on you're way to say extra grenades, it will reset to say sprint, just randomly tossing out perks since I don't know the order or what perks are dropped into which group). This occurs when your whole squad gets wiped out, which forces players to play more like a squad instead of lone wolfing it or running around like a bunch of idiots like the majority of the community does.