Hi Danny,
That list is, as Maurice said, from Bart Vanderveen's Bedford book. The reason for it giving production figures from 1940 and not late 1939, may well stem back to the British motor industries' system of starting production figures from around Autumn time, a bit like a financial year. I seem to recollect it might have been around August come to think of it, that would, for instance make 1940 figures go from Aug 39 to Aug 40. Just an idea.
Another problem I have noticed when trying to work out census numbers from chassis number on Bedfords. They never run in sequence and I believe this was because the census number was only allocated to the particular vehicle when it arrived at the RAOC Vehicle Depot. For lots of reasons, vehicles could be out of sequence in delivery, possibly due to rectification of defects at the factory, etc.