Confused about shortcode and settings values

As you can see in the Shortcode API, there is no jquery involved in evaluating shortcodes. Shortcodes are evaluated on the server side, in PHP, not on the client side with jquery.

It is entirely up to you what you do with attributes in the shortcode. If the user writes something like:

[demo speed=2000]

you would exctract that as an array in your plugin like this

$args = array ('speed' -> 2000);

But there’s no obligation to use $args in the plugins output. You could happily ignore it.

If you have a setting in your plugin that has the value of ‘speed’ as 500, you could decide to update it on evaluating the shortcode. In this way your site would ‘remember’ the value of the latest shortcode evaluation. Perhaps that’s useful for your purpose.

Summing up, you can do anything you like with the attributes of a shortcode.