After installing JSON-LD for SEO and checking your product pages in Google's Structured Data Testing tool, you may see results returned for multiple products, like this:
The most likely cause of this is that your theme's page markup contains existing schema.org markup in the form of Microdata (for more information on Microdata, see here).
Don't worry if you see this! In almost all cases, Google is able to recognise that the two sets of microdata relate to the same product, and will simply combine the data into a single product in their knowledge graph. If there are inconsistencies in the product data, or somethine else is wrong, you'll receive a warning about it in Google Webmaster Tools.
If you have further concerns about your markup, don't hesitate to contact us (firstname.lastname@example.org) and we'll help you out.