This question is going to be nigh impossible to answer, due to the differences in how various analytics platforms calculate their data.
If you're *really* interested in finding out where that discrepancy of 4 is coming from, you're welcome to have a supported user contact Customer Care and request a data feed for a particular day. Here's more information on requesting a data feed:
https://marketing.adobe.com/resources/help/en_US/sc/clickstream/datafeeds_configure.html
The data feed contains raw data for each day, which you can then compare with raw data obtained from your oracle database.