Er, the difference between the true headings of two intersecting runways is the same as the difference between their respective magnetic headings, is it not?
Can I come clean?
The old runway was marked 04, i.e. 040 degrees. The reciprocal was marked 22, i.e. 220 degrees.
The new runway is marked 03, i.e. 030 degrees. The reciprocal should have been marked 21, i.e. 210 degrees.
IT WAS MARKED 12.