Aha! That's why I always have a controlled crash when landing on 24R, I've been landing with 1° of drift!
It can't be the hump, one of the Prooners promised to bludgeon the hump into submission some time ago, and a Prooner wouldn't lie, would he/she?
As others have said, Runway numbers are rounded up or down to the nearest 10°, e.g. 232° with a Magnetic Variation change of -1° becomes 231°, and remains as Runway 23, similarly 239° becomes 238° and this Runway number is unchanged as 24. When the runway is midway between the two multiples of 10°, e.g. 235°, a 1° change will 'tip' the Runway direction in one direction or the other. A few runway numbers will change, many others will remain unchanged.
Regards,
Old Smokey