Why runways have numbers
The large white number at the end of a runway is not a name. It is a compass direction. The magnetic bearing of the runway is rounded to the nearest ten degrees and the last digit is dropped. A runway that points east, towards 090 degrees, is marked 09, and one that points west, 270 degrees, is marked 27. A pilot who lands on the runway marked 09 faces east, and that same strip seen from the other end is 27.
Every runway therefore has two numbers that differ by 18, because they are 180 degrees apart. When two or three runways run in the same direction, a letter is added: L for left, R for right and C for centre.
The pole moves
The numbers refer to magnetic north, and magnetic north does not stand still. Over decades the bearing of a runway drifts, and when it has changed enough to alter the rounded number, the airport repaints the marking. Several airports in different countries have renumbered a runway in this way. It is not a trivial job, because charts, lights, signs and procedures must all be changed on the same day.
The principle is practical. A pilot approaching an airfield can see at a glance whether the runway lines up with the heading on the compass.