Sexual Partner Count is the power to be able to see how many people an individual has had sexual intercourse with. Upon activating the power, anyone caught near its vicinity will have the number of sexual partners they have slept with 'burnt' onto their forehead.
There is no way to get rid of the number other than waiting for it to fade. If someone has intercourse whilst a number is on their forehead, it will increase by however many partners they have slept with in that time.