An Azure relational database service.
My databases also has the earliest PITR restore point by the end of August. And it makes sense. If memory serves, the default for PITR backups is to keep them for 35 days. Keep in mind that this is the earliest, so if you would need to restore the database per, say, Sept 17th, that should be possible.
If the database where the oldest possible PITR is only six days back, that's more puzzling if this database is as old as the other one. But maybe this is a newer database? Or it was actually restored six days ago.