You can find this: The next value is the number of miners, this must be the number of boards in cluster multiplied by 2
So if you have 2 bitburners, you have to choose the number 4:
--avalon-options 115200:4:10:35:380 --avalon-auto --queue 4 --bitburner-voltage 1285
No, it must be --avalon-options 115200:
2:10:35:380 --avalon-auto --queue 4 --bitburner-voltage 1285
Cgminer sees every board apart when it has an usb cable. The "total boards x2" number only applies when they are in a cluster (i.e. with canbus cable). Without it, it's just "2". (I think that is because a board originally had 10 chips on it.)