In our Site Explorer > Overview under the 'General' or 'Backlink profile' tab, you can see the URL rating distribution graph on the bottom right hand side of the page. 

URL Distribution graph shows you all the backlinks linking to the Target URL, sorted based by the backlink pages' UR (URL Rating).

In the above example, 9,915 (or 0.2%) backlinks coming to the Target URL has a UR of 10-19, and 1,107 (or 0.1%) from websites with UR 20-29 and so on.

Do also note that number of backlinks with UR less than 10 are only referenced as a footnote below the graph.