Usually what happens is the stick touches the side of the tube when checking and gets fluid on it giving a false reading.
Sometimes a slightly different bend on the tip of the stick can be of help, and is actually why I put a 90 degree twist right at the end of the stick.
This makes the edge of the stick hit the tube sides instead of the flat of it.
Also, if it were me I would go by the low reading because that is the one which is more likely.