How did I download 13 gig in less than 5 minutes?

I came home to d/l a large FREE file, actually 2 files(1 was 1.5 gig the other 13gig) from d****oid and then the internet went out, storms in the area, but once it was back up I checked me torrent progg, it said 'checking' for about 5 min..and then it was done!!!. 13 g in less than 5 min!! I have extracted the iso, havent installed yet but its physically ( digitally) there. Any ideas as to how and i guess more importantly how can i do dat chit again!! tnx in adv...