Could you check your quarantine settings especially "Days to store in Quarantine before deleting" Make sure to set the number days to keep messages in Spam Quarantine before deleting them. Shorten the retention period if quarantined messages are using too much of your system's disk space. However,
a shorter retention period increases the chance that users may have messages deleted before they have been checked. The default retention period is 7 days.
Reference : SBG Admin Guide.
regards,