Am I fasting wrong

I chose to do 16/8 1pm-9pm but I usually don’t go to 9 because I be full by 7pm so my body is used to doing 1-7pm Frfr . These last 2 days I’ve been eating until about 8:30 and I wanna know since my body is used to 7pm will that mess my fasting up or because it’s still in the 8 hour eating window it’s okay . I lost 4lbs in the first week but I just stepped on the scale and gained 3 lbs so I’m kind of confused on if what I was doing messed everything up