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Your settings are correct, but you need to consider a few things.

Quotas are always calculated against the backup records, not the backup archives on disk on or on remote storage. In other words, if you do not see a backup record in the Manage Backups page it is NOT taken into account when applying quotas. If you have files in OneDrive without a corresponding entry in Akeeba Backup's Manage Page you will have to remove it manually from OneDrive. This could happen, for example, if you had files stored from a different backup profile (including one that no longer exists), restored your site from an earlier backup (therefore the backup records for the backups taken since no longer exist in the database), or if you deleted some records from Manage Backups (which can also happen automatically depending on your obsolete records quota settings).

Furthermore, quotas will take into account only the backup record, without checking if the file exists. If a backup is listed as Remote in the Manage Backups page it participates in the quotas. This also means that if a backup record does not indicate it has remotely stored files it will not participate in quotas, therefore you will have to delete its files manually.

It is possible to change the backup profile's settings at any time. If you change the directory and move the backup files in the new directory, the older backup records will point to a location that is no longer available. As a result, these files will not be deleted automatically; you'll have to do it manually.

The quotas apply per backup profile. They will only take into account backup records in the same backup profile. If you have more than one backup profiles and set each one of them to keep three backups do keep in mind that this will keep three sets of backup archive files per profile.

Finally note that the quotas are only being applied at the end of a successful backup. They are not applied immediately. If you change your settings, old files will be removed after you take the next backup with that backup profile.