Do you have
PoolMath app? It may be easier for you to understand. What Marty and others have said is that based on your SWCG model if you only want to run at 14 hrs, you have to put output at 100% and will only generate 4ppm throughout that 14 hrs time period.
If you want 5ppm then you have to increase your runtime to 17hrs because you cannot increase your output above 100%.
If you want a lower output %, then you have to increase runtime even more - so 90% output will required 19 hrs to generate 5ppm over that 19 hrs.
The Pool Math app can provide you all the different settings based on what you want.
Also, the amount of PPM you want to generate is the estimated amount you will lose daily. So if you want a 5ppm FC target and you may lose 4ppm per day, then you want to understand what the you need to set your pump time and % output to handle 4ppm (not 5ppm).