If you're downloading a torrent that contains multiple files, for ex. 500mb worth, and you only select 250mb of it to download, will you only actually download 250mb or will it download all 500mb but only give you the files you asked for?

I've noticed in µTorrent that when you download a portion of a torrent under the size column it's still the original file size.
if you select do not download, it won't download. the reason why it says that its the same size is because that's what the torrent file that starts the download said it was.