Difference between $(Rev:r) and $(Rev:.r) in BuildNumber part of Azure DevOps Build Pipelines?

Was going through this doc Configure run or build numbers and found usage of both $(Rev:r) and $(Rev:.r) but no definition .r one.

Do anyone know difference between the two ?

Also checked a community issue Description of $(Rev:r) lacks meaning of $(Rev:.r) and its used on this page in most of examples raised regarding same, but did not find anysolution there too.

The difference is just having or not having an extra dot (.) character to the build number.

For example:

• If setting the build number the as $(Date:yyyyMMdd)$(Rev:.r), the result will look like 20231017.1.
• If setting the build number the as $(Date:yyyyMMdd)$(Rev:r), the result will look like 202310171.