If you are using a Blogger based website, chances are is that you are going to run into a speed issue sooner or later. While Blogger is extremely fast as it runs on Google servers, there is a very high possibility that your website is not following the best performance practices.
After you paste the code in and click compress a popup like the one above will appear. This is a form of light HTML compression that was made to prevent breaking Blogger functionality and I recommend all Bloggers using this form of compression.
The Blogger option is a lighter form of compression that is optimized to compress Blogger websites specifically. It is used to avoid breaking Blogger’s functionality.