That should be happening. In your book you will see that the cycle is brine draw + slow rinse. Once the check valve (typically under the salt at the bottom) starts sucking air, the valve blocks the path. However water continues to flow, and that is called the slow rinse.
The amount of brine is determined by the brine fill time along with its companion orifice (whatever its called) that determines the refill rate (often 0.5 GPM).