The leader board on the left is running tally of how many potential concerns may have gotten past the respective antivirus software tool. So, the higher the number, the more potential concerns could be sneaking through.
No, this is actually doesn't tell you anything about other AM vendors.
1. The most popular AV will get the top spot.
2. The numbers doesn''t mean that vendor X miss that huge number of malwares. It's possible that it's only the number of computers that got infected by the same malware.
Or a counter based on historical data rates. Kind of like the "real-time" death and birth numbers one can see in some museum of science. The counter also doesn't show how many infections are actually caught by the primary AVs and at the same time missed by MB. Sure, MB might find 1 pup that the AV missed; in the 100 infections that the AV caught. Meanwhile MB missed 99 infections that the AV caught and just decided to alert on "adobe-crack.dll" which might be a real crack that the AV decided to ignore (since not malicious to user). (Just because crack is malicious to the big corporate doesn't mean it's malicious to the user and AV's job is to protect the user and not financial interests of the big corporate)