Sometimes, while looking through domains/URLs on Site Explorer, you might come across pages that have a high UR, but low DR (like the above example).
Let's take a look at the definition of both UR and DR.
URL Rating (UR) is a metric that shows how strong a backlink profile of a target URL is on a scale from 1 to 100. Generally speaking, each page passes its rating score to all the pages that it links to.
Domain Rating (DR) is a metric that shows the strength of a given website’s overall backlink profile. Generally speaking, each domain splits its rating equally amongst the domains it links to.
Within the definitions lies the answer.
While they are both backlinks-based metrics, UR compares pages to pages, whereas DR compares domains to domains. They are not measured on the "same scale".
Therefore, a page with many high-UR links (therefore creating a high UR page) can exist within a low-DR domain.