Green checkmark (status 0)

Green checkmark with "info" badge (status 1)

Yellow triangle (status 2)

Red "do not enter" rectangle (status 3)

I suspect that status 0 indicates that they are investigating a problem with the server, and it switches to status 1 once the problem has been confirmed.

This is also a good example of poor icon design...they aren't self-explanatory, and so they should not be used.