This is only an implementation of the script created by Paul S. Randal to find what percentage of a database has changed since the last full backup. SQL Skills
Get the changes for the DBA database.
Get-DbaDbExtentDiff -SqlInstance SQL2016 -Database DBA
Get the changes for the DB01 database on multiple servers.
Get-DbaDbExtentDiff -SqlInstance $SQL2017N1, $SQL2017N2, $SQL2016 -Database DB01 -SqlCredential $Cred