Synchronous speed and RPM not matching

The synchronous speed and the RPM are not matching there is an additional factor of 2.
The RPM is 200 and the calculation of the frequency is N = 120f/p
p = number of pole pairs = 24
200 = 120 * f / 24
f = 40 Hz but if i measure the hall signal frequency it is 80Hz
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Please help me why is there a difference?

f / pp * 60 = 80 / 24 * 60 = 200

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