If you add a torrent, the size of the torrent file gets reserved until you delete the torrent from your cloud. Cloud storage used 1 point per 1 GiB. However, you will get the points back as soon you delete the torrent. The reserved points for torrent space will be shown as "Cloud Storage Space" in the Fair Use traffic history.
When your torrent is finished, you are able to download or stream the files. Only the files you actually download or stream will then use points - again 1 point for 1 GiB traffic.