On the Subject of Salts

I don't feel so good...

This module contains a Ghost which you must exorcise.

Take the sum of the digits in the serial number. Tap the Ghost a number of times equal to that sum divided by five, rounded down, plus one. You will then hear a small click. Then tap the Ghost a number of times equal to that sum modulo five, plus one. The module will not reset upon making a mistake, but you will need to input the correct answer to continue.