Not sure if this is a bug, or whether I'm misunderstanding how the "Backup" option works. I've set up a backup folder pair between my Nexus 5 and my PC, and transferred a huge swathe of photos from my phone to my computer. I then deleted the files from my phone (being careful not to delete the BitTorrent Sync system files), but the same files were subsequently deleted on my computer by BitTorrent Sync. Is this supposed to happen? I thought a "backup" folder pair meant one-way syncing, and that this wouldn't involve deleting any files on my PC. Thankfully I suspected this might happen a