The USB connector has a standard 5V supply connection.
That device looks like a USB to Serial (RS232) converter, and it looks like you have a choice of selecting 3.3V or 5V for the RS232 line supply.
As USB provides standard 5V, I'd imagine selecting that jumper, you'd bypass the 'buck converter' which would convert 5V - 3.3V
What are all the numbers on top of that 28 pin chip - the black thing with all the legs (pins)
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