How do I preserve the filesize of an MP4 edited in After Effects? I'm editing a small animation video (.mp4) of our app with After Effects (cropping composition to region of interest). I then add the composition to Adobe Media Encoder Queue and process it with the preset on my composition being Match source - High bitrate, encoded at H.264 as it's meant to be displayed on the web. Initially the filesize of the file is 8.3mb - after rendering, it's 30mb+ ! Why is this happening (I don't see how the quality can be better than it initially is) and what settings should I be using to export the .MP4 while keeping the video the same quality and a slightly lower filesize, as it should be?
In general, it's better to work with lossless, or at least, less lossy formats than MP4 if you're going to be re-editing the video.  If you can, work from a ProRes or Animation codec .mov file of the original file.  

When you export, adjust the bitrate of the video by entering specific bit rate numbers... Vimeo suggests between 10,000-20,000kbps for HD video.  Adjust it downwards until you get the output file size you want, but bear in mind the quality will reduce as the number goes down.