At Best Western in recent months, they put out a promo which was similarly worded, something like "earn triple points/miles on your second stay" with other (unclear) implications that it might only apply once.

A month or so later (after I'd bypassed using the promo because it didn't seem worth it if it only applied once), they reworded it to make clear that you "earn triple points/miles starting with your second stay and every stay thereafter" (during the promo period).

But they lost out on some my business because they took so long to clarify that it was a worthwhile promo!