Example of shortcode?

Hi there, i was wondering if someone could give me an example of inserting the optional shortcode options? I can’t seem to find an example online or in the widget home page.

For example I want to be able to display small images, so would it be:

[SI_FEED_SIZE_SMALL]??

Thanks for your help,
Des

https://www.ads-software.com/plugins/simple-instagram/