The smaller the file, the lower the quality.
If you want smaller, don't use the High Quality setting, but use Low Quality.
It is either or in this case. Either a smaller footprint and lower quality, or a larger footprint and a higher quality.
If you don't export at all, the footprint will be as small as you can get, nil.
Thank you very much for your fast reply!
Could you tell me where and how I can set to Low Quality? Well, I only see a bunch of lines of High Qualities..