This is an experimental enhancement to the Version Checker. Now each time the master TBX is exported to HTML (excluding HTML view-based exports), a counter is incremented. Using a similar $AutoFetch system to the Version Checker the user's local TBX can check if a new TBX has been issued. If a new version is released, checked by comparing $MyVersion with that of the version checker, the build counter is reset to zero. Thus each version starts a new build number sequence.
The Rule used for he checker is long and so is stored is a code-style note in the /UTILS section. That note sets the Checker note's $Rule.
The term 'build' relates entirely to aTbRef updates and does not imply anything about the status of Tinderbox itself - see the Version Checker for that aspect. The build tracking allows active users of local TBX versions of this file to keep up with the fairly constant trickle of additions and corrections to the aTbRef corpus that occur within the lifetime of a single Tinderbox version.
Due to local testing, etc., the 'live' build numbers will not necessarily be in strict sequence - though they will always increase during the life of any given TB version.
The note has the download URL for the master TBX file's ZIP file displayed as a key attribute - click the globe next to $MyURL.