Download usage refers to the data (i.e. files are made up of potentially millions to billions of bytes of data) sent over the internet in an attempt to preview1 or download your files from our servers. Keep in mind that your files can be downloaded multiple times by the same recipient (e.g. if they shared their link with another person). The Activity tab located at the top right of your files provide details on how many times each recipient/participant clicked the download link, etc.
The download numbers come directly from our hosting partner Amazon AWS (an Amazon company) and are the same numbers that appear on our bill from them. Under ideal circumstances, downloading from a good quality internet connection and staying within the same continent as the file server, it would take a little over 100% of the file size to download a file (due to the costs of HTTPS encryption and other standard protocol overheads).
If you uploaded a 10GB file and sent it to 10 recipients who each downloaded the file once, you would be charged for 100GB of downloads.
If you were to cancel a 1 gigabyte download 10% of the way through, we would charge you for the ~10% of bytes sent (roughly 100 megabytes).
Additional each link to download a file can be used multiple times. For example, Firefox, Chrome and IE allow users to pause and resume downloads often resulting in an overlap of downloaded data. Web browsers and especially Download Managers (e.g. DownThemAll, FlashGet, or cURL) can also use a link to start multiple downloads for the same file, this can dramatically improve download performance but often results in additional downloads