trouble finding source for mail-notification on i386

["Tim Olsen" <tolsen718@gmail.com>]

The latest source for mail-notification has a version number of 3.0.dfsg.1-7

However, the latest i386 binary for mail-notification has a version
number of 3.0.dfsg.1-7+b1

What does the extra +b1 mean?  How do I recreate the i386 build of
mail-notification?

thanks,
Tim