I wanted incremental build numbers from VisualStudio online when automatically building and deploying to Google play store.
The build process file creates the buildnumber in the first line:
The $(Rev:xxx) defines the build number. When a build is completed, if nothing else in the build number has changed, the Rev integer value is incremented by one.
Although I could not find any documentation, it seems the Rev number has the following format:
rr formats it like ## so:
$(Rev:.r) is formatted as .1
$(Rev:.rr) is formatted as .01
$(Rev:rr) is formatted as 01