/dev/cu.usbmodem incrementing trailing number

I have a friend who is having an issue. It seems every time he flashes his device (Electron, I believe), the trailing device number increments by one on his Mac laptop. He apparently is forced to unplug and plug-in the USB cable to get things to work. I don’t see this on my MacBook Pro. Any thoughts?

I do see it with Arduino boards as well, though.