The number module displays information about the signal itês receiving from your other modules. It has two modes: in -value" mode, it displays a number from 0 to 99 on its LED display, where 0 is totally off, and 99 is all the way on. In -volts" mode, it displays the actual voltage on the signal pin, from 0.0 to 5.0 volts. It takes the same signal it receives and sends it out to the next module.