The objects in Sqlserver custom checkpoints are being detected/discovered with object.minutes.default.0 extension
The 0 after the object references the order of the threshold schedule policy.
At the custom checkpoint, you can create multiple threshold schedule policies for the same object as below screenshots:
and I selected the db.name as the Key column Name and its value is dbname as below:
When I go to the status tab, I can see 4 policies referenced (0,1,2 and 3) times the number of databases ( except the excluded).