There are several reasons why a snapshot size can be smaller in comparison to the data usage you see in the Microsoft admin panel, especially when it comes to OneDrive and SharePoint.

Among these reasons are the following:

  • Keepit does not cover versioning of files
    This applies to both OneDrive and SharePoint which have versioning. Keepit backs up only the current versions of files, so, for example, if you have a file that has 3 versions, each of which takes up about 100Mb, then in Microsoft you will see 300Mb, while in Keepit you will see just 100Mb. 

  • Skipped files due to Microsoft throttling or lost connection
    Keepit may not have been able to receive from Microsoft certain data that it tried to access. When this happens, Keepit attempts to back up the skipped files in the next backup jobs.

  • Keepit may not cover certain data types or metadata
    The amount of data you see in Microsoft is not always an accurate representation of the data you have selected to back up. Certain metadata that is stored in Microsoft as well as certain data types may not be covered by Keepit. For an overview of what data we cover, see: What data can be backed up?

See also: How to calculate the amount of data you have in Office 365