+1 stone rose - go until you have one more than you have now
1 stone rose - go until you have 1 stone rose - which means stop immediately if you already have it.
You say you "had it as a condition". Can you elaborate, please?
I'm guessing the default condition for the oasis was activated which is, IIRC, +1 stone rose. I've never really understood why it was +1 and not just 1.
The other fun thing about this is that, as a quest item, after it leaves your inventory, the default goal for the area is still 1 stone rose... even though it will never happen again during this ascension. But that's on you...