This depends on how you have your BIOS boot configuration set up and whether you have a USB stick or USB DVD drive plugged in. I installed with the single USB key option and the correct number for me was 81. If you type 80 and press enter it will show the names of any bootable drives below. If your installed partition does not show, press ESC and enter 81, then see what bootable drives appear below. If not the correct installed partition, hit ESC and try 82. OSX86 is not as easy as a real Mac, and Apple deserves the money they make for making it easy as pie. OSX86 takes a lot of reading, Googling, and some know-how, but there are those of us who are addicted to such tinkering.
Dell Mini 9 - 16GB STEC SSD, 1GB RAM - No webcam, no bluetooth, no WWAN
Dell Mini 9 - 16GB STEC SSD, 2GB RAM - 1.3MP webcam, BT, no WWAN