Silver Puppy Question...PPM

I am new to making CS. I made my first batch in a pint jar. It took 3 hours. It tested 7 PPM. It was Crystal C.. I made my second batch in a quart jar. It took 11.5 hours, tested 7 PPM and was a very, very light yellow.

The water tested 0 before making. I would like to make 20PPM. My understaanding is in order to get greater PPM you run the Silver Puppy on manual for as long as it takes. Isn't 11.5 hours to get 7PPM a little long? Plus isn't one of reasons it turns yellow is because of the length of time run? How can I get 20 PPM without running it 24 hours and without it turning yellow? I have a magnetic stirrer.

Thank you for your help!