1.5 Gb for 7 sec video (after effects) why?

So after effects 6, for a video of 7 second it makes me a file of 1.29 gb.. what am i supposed to do with it?
The most of the times i was converting the file from avi to avi with format factory and the video became about 20 mb.. same quality..

But now i am in windows 8 freemake crashes, format factory make the video 2 mb with a very bad video quality, and any video converter the same with format factory..
what am i supposed to do?

via Video Editing Forums: Digital Director – Adobe Premiere, Premiere Elements, and After Effects http://www.videoforums.co.uk/adobe-premiere-premiere-elements-after-effects/42349-1-5-gb-7-sec-video-after-effects-why.html