I was sitting on concrete on an airfiled in a wirbelwind and vehicle supplies were out. From the gunners position I sent a friendly a check six warning using the ' key. The check six was sent but I was back in the drivers position, I had been reloaded and the supplies were all gone. Now as far as the supplies being gone, maybe it used the last box to reload me. I don't know.
But whether it use one box or all of them, it shouldn't do that just by sending a check six.
This has happened to me before. I haven't tried it in a tank yet, just the wirbel.