I think both are correct, depending on the production year of the watch
By: w220 : September 4th, 2019-05:53
I believe the 330 and 315 movements were first introduced with 29 jewels. Then it was changed to 30, and then later back to 29 again. I guess they went back and forth what is the best material to use at the position where the 30th jewel may be.