So about those US-10 exit numbers. I actually emailed WIDOT about this last week. I got a response today. I am not going to quote it directly but they went back and looked at planning documents from the late 80s for when US-10 first was planned to be a freeway/expressway in the "eastern part of the state."
And the long and short of it is, they really don't know! It could be a simple miscalculation by the original planners. But since then they have used the exit numbers that correspond to this initial exits, which is why everything is off by about 50 miles. So the mystery continues...