I think that the 20% steady is a fault code, unless you have a car originally delivered in California.
I have a few sheets of paper with these fault codes buried somewhere, but I'm not sure that I can find them. I will look.
I expect that the fault codes are on the CD, if you have one or can get someone to send them to you. 10% constant indicates one thing, 20% constant indicates another thing, etc.,
PS, that's an incredible meter for $30 isn't it? LB