The whole thing really is beyond my comprehension.
In conversation with friends (who generally aren't couch potatoes and one or two of whom cycle) I mention that someone is having a crack at this record and then ask them what they think the existing record is.
Answers are generally in the 20,000 - 30,000 mark, after some careful consideration.
When I give them the actual figure the initial response is one of surprise, followed by a few moments of deep thought, and then, when they've translated this into a daily mileage figure, one of utter disbelief. I have to say that that's how I first viewed it too.