netflow graphs

[VEbzuT6X]

Probably a stupid question but i'm not sure what i'm looking at.

Most of the ports i'm seeing usage on are ports i've open.  The 27***'s are steam, i've got 7k through 9k open for rocket league, but 10000?  That's not a port i've enable access to, it's not in any of my aliases, etc, so why's it showing up in the graph?

Does this graph show port usage from both directions?