DNA Center has a versioning scheme that uses four digits. At the time of writing the recommended DNAC version is 2.2.3.6

 2.b.c.d - The first digit is the major release which introduces “significat market value, including infrastructure and architectural changes”
 a.2.c.d - The second digit is a minor version that includes “new functions and features in the platform”. It is categorized as a “new market value” release and also an anchor point for long-lived releases
 a.b.3.d - Third digit represents “new functions in applications” and it is categorized as a “minor-minor” release
 a.b.c.6 - Fouth digit is the patch level. You should only see bug fixes for these releases, but Cisco states that you could see “enhancements to existing functions introduced in a previous feature release”, which i interpret as enhancements from a “minor-minor” release

You can find the official document for these version numbers here:

Software Lifecycle Support Statement - DNA Center

Table of DNAC Version Code Names

You are likely to run into version code names in the Bug Search Tools

Here is a table with version to code names: