That, Sandy, is the BIOS recognizing the internal ID of the monitor in sequence. The earlier the model of monitor (or sequence ID) the more priority the bios places on that as the primary output device. I see that in Windows a lot as well... a newly imaged machine often (50/50) will place the "primary" monitor on the wrong side until someone goes into the display properties and drags the wanted monitor to the left side of the dialog window.