The output file size depends on the duration of the movie, the video bit rate and the codec you select for the output file. You can set a lower bit rate for a smaller file size. Please notice that the quality of the output file will be less desirable with lower bit rate, but you can select a proper bit rate after some tests of the conversion.
This FAQ is about: Frequently Asked Questions, PowerPoint to FLV Converter, PowerPoint to iPad Converter, PowerPoint to Video Pro, PowerPoint to YouTube Converter