Once you hit 140 nights after the May 23 cruise, call Seabourn and ask to have your free week bonus credited to the October cruise. They'll tell you how to get this accomplished - I'm not sure but I think I had to send someone an email.
Seabourn will credit you for 7 days on the October voyage by calculating the cost on the October voyage for the average of the cabins you paid up front to sail in - no upgrade or upsell credit goes into the calculation So, if you typically paid for V3 cabins, they will credit you for the cost of a week in a V3 cabin on that cruise.
We have another free week coming, but we are probably not going to use it on our next cruise because we got a ridiculously low weekly price for 5 weeks on board so will save our free week for another 2-week cruise we booked where the weekly rate is much higher.
Hope this helps.
Linda