The storage space that a file uses in Google Drive on the web may differ from the amount of space it takes on your computer’s hard drive. Differences online and on your local hard drive typically happen when there are multiple versions of the same file or someone shared a file with you.
When there are multiple versions of a file, more storage space is used in Google Drive on the web than on your computer.
This is because Google Drive on the web stores all past versions of a file. Versions that you've chosen not to automatically delete take up storage space. The Google Drive folder on your computer stores and allows you access only the most recent version of a file.
Files that someone has shared with you don’t take up storage space in Google Drive on the web. If you’ve chosen to sync anything shared with you to the Google Drive folder on your computer, they’ll take up storage space on your computer’s hard drive.