The Ribos node number difference is an FS1 cbani inconsistency. The Arcadia is described as being present in major systems (although it's not entirely exclusive) in the FS1 tech description, and Tombaugh station (Ribos) appears to be a significant military research centre as the Taranis and shield systems are taken/originate from there. Ikeya doesn't have much info, but is identified as a Shivan entry point/beachhead; to all extents and purposes it seems to be a bit of a fringe sector, as the FS1 briefs have less mention of any fleet presence there (Ikeya seems to be a prime system for any campaign focusing on mysterious goings on or Shivan attacks). Neither system makes it into FS2 briefings.