Most of these seem self explanatory, however I'm confused about the last column. It doesn't seem consistent. I've searched for and read the documentation I've found on bounties both here on askubuntu meta and in the help but have found nothing that explains this column.
Here's what I'm talking about:
As you can see in this image of Mateo Bounties Earned the final column has a date and a name. What does the name indicate? You'll note that while more than 1/2 of them pictured have Mateo listed, three of them have other names. Why is that?