Display Message Options?

When I ran the latest update pushed out for 11.2.4 MU1, the reboot message showed the countdown timer in the displayed message. The {0} was placed in the message to get the countdown time to show up which is really slick. I was wondering if there were additional options to this process that could be used? I looked through the documentation as best I could over the weekend but couldn't find anything. Something that would be nice to display within a message would be something like

{Bundle_Name} or possibly others.

Does anyone one know of further options that can be placed within messages like this? Did I miss this in the documentation somewhere?

Thanks

Richard