Simple Questions?

When I make changes (add delete change) on the desktop Sydrive Folder (on MacOS) does the upload software upload all the files, including the unchanged ones, or just the incremental change? If a folder has changed, in the sense that a new file has been added, does the whole folder get uploaded or just the new file within that folder?

While the upload is taking place the drop down menu from the Skydrive icon at the top of the screen displays something like "Uploading N files and the XMB of YMB". What exactly does this mean. How is it calculated?

Thanks