After updating Exchange or installing a cumulative update, you may be using the get-exchange server command to check if the server was properly update. If so, you may be surprised to learn that not only did the update not apply, but you may be several builds behind, according to the build numbers.
No need to worry, that command will display the Exchange AdminDisplayVersion, which is not what you are looking for. To get the exact build number, you can either run the Exchange health script or use exsetup by copy/pasting the command below. This will display the exact build number you are looking for.
Get-Command Exsetup.exe | ForEach {$_.FileVersionInfo}