Bedtime mode starts 9 hours before your set wake up time. So since you set it for 4:30 AM, you will see your Bedtime mode color temperature at 7:30 PM. The reason why it's 9 hours is, you want to begin avoiding blue light during the last couple of hours of your day before you go to sleep so that your melatonin production isn't interrupted.
If you don't want this, then set the Bedtime mode to be the same exact color temperature as your Daytime mode. That way, you won't notice Bedtime mode turning on. All you will see is the color temperature changing for Night mode. I don't use the automatic function of f.lux, but I used to years ago. If I recall correctly, I think Night mode starts about a half an hour before sunset, and finishes about a half an hour later.
