It assumes a 50 week work-year, and that the "Other Miles" happen every day of the year, rain or shine.
The default bicyclist efficiency of 45 calories per mile is controversial and dependant on a lot of variables: weight, cruising speed, density of traffic stops, wind, hills, you get the idea. I found a lot of conflicting information, most of it for racers who don't stop at stop signs or lights because this really ups the power required. Links: