Perhaps you have your own tracker through this.
Your files don't necessarily need to be sync'd with all devices, but each device have different files tracked. This service may gave us our own 'Tracker' that would index our 'cloud' files that you pick which you want downloaded, of course, going through BitTorrent's service. So it would be true, the max file size/capacity would be the combined capacity of your devices. As long as your device is on and connected to the internet, you could retrieve that file, and the track would advise you if the file is available or not