The buy button code that is generated for each of your products includes a tracking pixel. The tracking pixel is the part of the button code that is responsible for tracking the stats on your visitors. It is required to have the tracking pixel in place for your product to be approved.
Below is a sample button code.
<a href="https://www.jvzoo.com/b/32825/169548/1"><img src="https://i.jvzoo.com/32825/169548/1" alt="Customer Support" border="0" /></a>
The first URL leads the buy button click to the check out page. The second URL in bold is the tracking pixel. The tracking pixel allows the JVZoo system to calculate the stats on the Sales Report. You can find the Sales Report here.
For more information on setting up your buy buttons you can read the following article: Setting up your Buy Buttons