Remember, if you already have a USB stic inserted in the 'bottom usb port', that one will show as USB1 as long as you have no other inserted at startup.
If you add another stick in upper front after the startup and usb at bottom are in use, that one at top will automaticly show up as USB2.
If upper front is inserted and also bottom are in use while startup, the upper will show as USB1 and bottom as USB2.
Myself I have a 'permanent' connected USB stick at bottom, and always startup with the other ports empty 'till startup finished. (as long as there is no OS update to do).
That way bottom port always will show as USB1.