An average lean body mass is pretty much a useless number for comparison due to everyone being different heights and compositions. There are many references a quick search will bring up for body fat percentages.
For starters, men and women have different levels of essential fat. This is effectively a minimum level of body fat, below which health problems can arise such as issues with menstruation in women. Bodybuilders try to be as close to this as possible for competitions, but do not maintain it for their health. This is around 3-5% for men and 8-12% for women.
Athletes tend to sit around 5-12% for men, and 12-20% for women.
And up to ~24% for men, and ~30% for women is considered healthy.
Above this is generally considered obese.
When it comes to body fat tests however (glad to see you understand there can be significant errors), they are generally better used as a measure of change, especially home tests, due to various factors such as distribution of fat, types of fat etc.