I have my dimmer switches set to slowly dim up for about 5 seconds. So when I turn them on, it takes 5 seconds to go from 0% to 100%. Works great.
However, on some of my switches, I have them set to lower brightness. I have one switch that I often have set as low as 20%. If I have the bulb set to 20%, it takes 5 seconds to go from 0% to 20%. The switch should scale the time based on 100%… so it should only take 1 second to reach 20%, not the full 5 seconds.