Google Photos Backup creates large Pictures/GPBackup folder

I installed Google Photos Backups on OSX (Mavericks). It created a /Users/rob/Pictures/GPBackup folder that is 10 gig in size, and it looks like it has copies of all my photos and movies. I don't want it to use all this space, but didn't see any configuration settings for this. What is the purpose of this folder? If I just delete it, will Google Photos Backup continue to work?

If you click the "Google Photos Backup" icon in your menu bar (looks like a gray pinwheel), you should see the "Preferences" option. Clicking this will open the preferences window. There you should see a checkbox for "Also copy photos/videos from external media to" (See image below). Uncheck this box and you shouldn't have the extra backups anymore.