You are right Blue! I called the 800 # again spoke to a different gal (the first gal was not too helpful). She told me exactly what you posted. They sell a certain amount of tickets for each tour online then when those tickets are soldout it goes from Reserve Now to Inquire Onboard.
She also said to go right to the excursions desk when the ship sets sail because it can sell out at that point.
They do keep tickets available onboard for those cruisers that don't book online or have access to a computer.
I feel better now!
I'll just run over there at 5pm and buy the ticket.
The excursion is the Zipline Canopy Tour in San Juan. Being I thought it was soldout with Royal I contacted the tour and they quoted me a price of $125. Royal sells it for $127. The ship is in San Juan only from 8 to 2 so I would not venture on this tour on my own just in case something happened and I did not get back to the ship on time. At least doing this tour thru Royal the ship will wait if there are any delays. 8)