OpenGraph structured data listed as "Unspecified Type" in Google SDTT

This is my first time working with structured data, so I'm not sure if this is even an issue, but when I run the Structured Data Testing Tool, I get 3 sets a data showing up like so:

Now Article and WebSite are correct, but at the top it says unspecified type. Now when I view that section I get this:

This seems to be loaded from all of my og:tags. I am specifying the type like so:

<meta property="og:type" content="WebSite"/>

but it’s still coming in as "Unspecified Type".

Is this correct? Is this something I need to worry about? If so, how can I fix this?

It’s not a problem that needs solving. The report in the SDTT is correct (there is no type specified), but that is expected when using the OGP vocabulary.

Usually, a vocabulary has classes/types (like Person) and properties (like name), but OGP only has properties, which is somewhat unusual.

While OGP defines a type property, its value is just a string (like "website"), not an actual RDF class. In RDFa, classes would be specified within the typeof attribute.

A consumer specifically expecting the use of the OGP vocabulary will cope with this. Such a consumer might assume that OGP properties in a document are always about that document.

(Question about the same topic on Webmasters SE: Tag property og:type not recognized by the Structured Data Tool; my answer contains more details there.)