It means they are spawned units. I have played around with what a unit has spawned, so a spawned unit either way has the white flag, even a units that spawned from a spawned unit. There is a limit actually, and it is usually small(with exception of the ISD) I believe there is a limit on land garrison, I think it is how much credits you currently have.
Sig made by Princess Lyla
The Sith will always be around as long as there is hate in the Galaxy.
Dark Hands of the Empire(Clan Member)