Up to three category levels can be returned, and will be separated by a forward slash ("/"). For example the returned category might be US/CA/SFO.
string
Coverage
A score from 0.0 to 1.0 that indicates the percentage of pages in the requested language that belong to a particular domain out of all the pages that Bing has indexed for the same language your website's domain.
In other words coverage is the percentage of webpages that match a category and language divided by the total number of webpages using the same language in the domain.
For example, if the category US/CA/SFO matches 500 english webpages and US/CA matches 1,000 english webpages, then the coverage will be 0.50 (50 percent).