[Plugin: Advanced Custom Fields] Deleted subfields remain the DB

Hi,
I’ve bought the repeater option and used it to declare a series of dates.
If I add X dates to the post and save it, everything’s fine. If I edit the post removing a date from the series, in the DB (table “postmeta”) the date is still present.
It’s a big problem since I have to find at once which post has a date subfield set to a certain day, so I have to check these values, but I have to do it with a custom SQL query and I can’t use your repeater functions.

Why the deleted subfield is not removed from the DB?
This would also mean that if I frequently change the subfields, all the old values still remain in the DB, totally unused?

https://www.ads-software.com/extend/plugins/advanced-custom-fields/