Default font size on the status bar
I'd guess at 11pt, SanFransisco.

Standard list views are 12pt, the headers are smaller, but not small enough to be 10.

You can test by eye...

Open any finder window
Hit  Cmd ⌘   J 
Change the text size until it appears to match the status bar.
Zooming the screen might help comparison [ Opt ⌥  + scroll wheel by default]

This is a quick attempt at matching, artificially zoomed in Photoshop...