Another thing to pay attention to if you haven't already noticed, torrents only stay freeleech for a given time period.
So if you don't complete a freeleech torrent within it's freeleech time duration, you'll get "charged" for the rest of it.
The entire torrent isn't freeleech in some cases.

Hello, not to hijack the thread, but what is your avatar from?

Most (and maybe all) download will be ignored but people may be caught by the 30 minute interval between 'announces' and end of freeleech

Only slightly off-topic. If you start downloading a new freeleech and it says this will take years, hang on for a while. A couple I started like that had loads of people sharing within a few minutes and I completed well within the freeleech period

The tracker adds up the reports (called in bit torrent slang "announcements") from the peers torrent client:

• A first announcing to have joint the swarm, so that the tracker can give the IP to the other peers at their respective announcements. Of course the reported UL and DL at that first announce is zero.

  • From then each 30 minutes (this is our tracker setting, other trackers may ask for different intervals, but 30 minutes ius a quite common setting) it reports to the tracker the UL and DL, and gets back from the tracker the available peers. The countdown to the next announcement can be seen in the torrent client. E.g. µTorrent > "Trackers" tab > "Update in" column.
  • When the client finish the download, it makes an announcement out of order
  • If the torrent is stopped (not just paused), the client makes an announcement, too.

  So all depends on the moments of these reports:

  • All downloads announced during the free period won't count on freeleech torrents.
  • All downloads announced after the free period will be counted. This includes the download since the last announcement in the freeleech period and therefore a part of the free download.

  Therefore the to make sure no download is count, the download needs to be finished within the free period.

  To avoid that "free" download is count, because reported after the free period, a possible method is to stop the torrent just before the end of the free time, which will generate an out of order report to the tracker.

  I try here below to show this with a timeline on canonmc's question / example:

  end of DL ->|
       |<-30min.->|      end of free time->| |
  …---|----------|----------|----------|----------|---...
       |  55 MB   |  60 MB   |  55 MB   |  | |
                                20 MB ->|  |<-
                                         ->| |<- 10 MB

  In above timeline example, three of the 30 minutes interval downloads happen fully during the free period with 55, 60 and another 55 MB of download, a total of 170 MB

  During the next 30 minutes interval, the free time ends and until it 20 MB were downloaded. Then after another 10 MB download, it is completed, total download 200 MB. At the moment of completing, the torrent client reports the download since the last announcement, the 20 MB plus the 10 MB = 30 MB.

  So in the above example 170 MB were free and 30 MB were counted by the tracker as download.

Say, for instance, I start downloading a 200MB freeleech torrent. At the end of the freeleech period I have managed to download 190MB of the file but I carry on to complete the download.

Would my download show for that file as 200MB or 10MB? Those worried about their ratio (wish they didn't have to be) might not want to start a download if they were going to be whacked with the full download if they missed the freeleech time limit.

And is there any way to extend the freeleech periods. I made one torrent a freeleech but the download was so slow a lot of people were not able to complete within the 24 hours. I was happy to spend more points but couldn't find a way of doing it.

"[LYLY75] …" size: 952.70 MB

Which was made freeleech 2014-02-28 12:25:18 - 24 hours freeleech added  (means until 2014-03-01 12:25:17)

and you completed 2014-03-01 12:40:06, means about 15 minutes after it wasn't any more freeleech.

If it downloaded in 5 minutes as you say, which is very well possible, because a freeleech torrent got many seeder, the torrent client reported the full size download to the tracker at the time it completed the download, i.e. after the freeleech period.

That corresponds exactly to the global download in your Profile statistics of 952.70 MB

HOWEVER, when the file is no longer a freeleech, your ration can be affected negatively, as at that point, you are downloading a file that is not freeleech.