For more details see the Rich Snippets extension page.
See an example of the website with Product, Review Rating, Breadcrumbs and Organization snippets in the search results.
Price Including Tax - In search results you can display the product price including tax or the price excluding tax.
Show Total Count for - You can choose whether to display votes or reviews, or both votes and reviews at the same time on Google search page.
Enabled - See how to configure organization mark up here http://support.google.com/webmasters/answer/146861
Category Page - This feature lets you display the average product rating and minimal price in search results as well as at the bottom of each category page on your site.
Enabled - Enable the feature if you want to display additional info in your tweets
Description Length - Specify product description length, which will be automatically loaded from a product page. Set image parameters, minimum 160*160 px
Second Field Value - Choose which info you want to show: price, stock availability, rating or custom text field (in which you can write anything, e.g. info about a discount). Give any label you want.