That Rob is talking about his eyesight before correction. Thus is not legally blind. It is possible to have correctable 20/400 vision.
In fact, using a very handy page I just found, I would estimate Rob is probably not very myopic at all (if it myopia) - probably only about -3 diopters or so. With just me here it's hard to check, but I would estimate from the same page that I'm probably 20/2000 or so. Next time I have another person to hand I shall have to check.