Store views are a record of pages served by the Shopalyst system, where as the Audience events/Audience lists/Custom Audiences are an outcome of the corresponding tags being fired from the Shopalyst landing page (examples include Facebook Pixel and Adwords Tag on Google).
Based on user interactions on the landing page, events like STORE_VIEW, PRODUCT_PAGE_VIEW and CONVERSION are fired using the audience tags and pixels for the brand. There will be differences in the audience count and the store views owing to factors like network losses, latency in the tag serving/recipient systems, browser settings, and cookie consent among others.
The differences could also be owing to variations in the approaches that media platforms use to capture audience data from web-site visits. Click these links for more details on the approaches used by Facebook and Google.