Shrink Database: After a while the database will get bigger than necessary. This command will shrink it back to it's minimum size. This happens automatically every 5 times you open RoasterThing, but if you want to do it before backing up the file or uploading a copy this is what you'd do.
Renumber Database: If you're tired of gaps in the Coffee or Roast numbers because you've deleted some, this will renumber everything starting at 1 keeping the same order. There is no reason to ever do this. I don't believe it will cause any problems, but I would highly recommend backing up your data before doing this.
Rebuild Indexes: There are some indexes that help RoasterThing do a better job of sorting the data. If things seem out of whack, you may try this and there is a small possibility it will help. In the past I wrote in a different language and it was a requirement that a command like this exist. I'm not sure that there is any point to it here, but it causes no harm so here it is.
Update VDB3 File: When you install Version 3 on a machine that has a working Version 2 install the first time you run Version 3 it should automatically convert your Version 2 data(VDB3) to the new format(VDB4). If you have more than one file you want to look at that came from Version 2 you'll need to convert them individually using this option.