Board Thread:Questions and Answers/@comment-29342734-20170427202621/@comment-1038387-20170430201443

3601 was discovered later. It's 3600 sectors in known space - there is room for more beyond it, which is where 3601 is. As for the 0 discrepancy... Technically, Oa is in all sectors, as thesectors wedge out from it (except, of course, 3601).

There was a much earlier instance though, before the 3600 number became fixed, of a sector 5152A or something. It was later changed to 3152 or some such.