Your system just needs to be calibrated. When everything is all set, it should be perfectly level. If you are using the popular HWH 625 series leveling system there's a "how to do it" tutorial at
www.rvtechlibrary.com/chassis/leveling.htm that you might want to take a look at.
Today's RV fridges aren't all that picky when it comes to how level they are so you have a fair amount of tolerance. My personal choice is to place the level vertically on the bathroom door hinge, level the coach manually, then adjust the sensor. That way the door won't swing open or closed on it's own when parked.