;-) I'm not sure of the particulars of that controller, but in general there can be eight devices on a SCSI bus. Mind you, the controller itself counts as one of them, so you're left with seven drives, scanners, etcetera to add on.
Each device needs a unique number between zero and seven. (Seven is usually the controller itself, but not always.)
Also, the appliances must be connected in series, with no "Y" branches allowed.