Metal DC Geared Motor w/Encoder - 6V 210RPM 10Kg.cm (FIT0521)

Both are probably correct. From the product page:

Hall Resolution: Hall Resolution 11x Precision Reduction Ratio 34.02 = 341.2PPR

I’d say there are 10 sections in the encoder set at 36° on the motor shaft, but one full revolution of 360° triggers the first one twice, giving 11 counts per single revolution.