and... what happens when the runaway has a heading of 36 degrees?
The true heading doesn't matter, the runway numbers are based on magnetic heading so it would depend on the amount of declination. If it were 36 degrees magnetic then the runway would be 4.
(In International Civil Aviation Organization (ICAO) and some United States military (such as Edwards Air Force Base) airports, numbers for runways less than 100° include the leading "zero", for example, Runway Zero Two or Runway Zero One Left. However in the United States at most civil aviation airports, numbers for runways less than 100° are often given as single digits)