There are two concepts that need to be differentiated: upload units and files stored.
Under the Upload units counter we show the number of upload units for the current month, as we bill for upload units. An upload unit is a file of size less than 100 MB or a 100 MB chunk of a bigger file. For example, uploading a video file of size 350 MB consumes 4 upload units.
In Files Stored counter, we show the total number of files, that are stored.