The author stylesheet specified in tag script is too long - document contains 21759 bytes whereas the limit is 10000 bytes

Amp Validation Error: The author stylesheet specified in tag 'script' is too long - document contains 21759 bytes whereas the limit is 10000 bytes.

If you are trying to validate your AMP HTML webpage and you see the above validation error that it means that you have exceeded the set limit that a javaScript amp-script code you can have for a page.

amp-script is the way you can run JavaScript on AMP-enabled webpages, but there is a set limit,

amp-script has the following restrictions on JavaScript file size:

Maximum of 10,000 bytes per amp-script element that uses a local script via script[type=text/plain][target=amp-script]. Maximum total of 150,000 bytes for all amp-script elements on the page.

Source: https://amp.dev/documentation/components/amp-script/#faq

1. You need to remove unwanted javaScript code, try and re-write your code to make it fit 10000 bytes. If you are external libraries like bootstrap or any other UI framework, you may have to avoid it - or use alternatives.
2. You can minify your JavaScript and CSS code - this really helps.