Allow set custom number to syc at once from 1 to some maximum.
At the moment you get something like eight or so files syncing at once, all fighting for the limited upload speed better to only sync one or two massive files at once and queue the others. This is important for massive gigabyte files because faster they are copied in their entirety then they are same if something goes wrong don't want a massive file to have to start from the beginning. It also means the computer file can be shared faster rather than split the upload capacity between lots of files that are all uploading together. If it's customizable then a user can tailor how many depending on her internet upload speed and file size.