Apache Portable Runtime
The following attempts to show the relation of the various constants
used for mapping APR Status codes.

  0          
 20,000     APR_OS_START_ERROR

   + APR_OS_ERRSPACE_SIZE (50,000)
 70,000      APR_OS_START_STATUS

   + APR_OS_ERRSPACE_SIZE - APR_UTIL_ERRSPACE_SIZE (30,000)
100,000      APR_UTIL_START_STATUS

    + APR_UTIL_ERRSPACE_SIZE (20,000)
120,000      APR_OS_START_USERERR

    + 10 x APR_OS_ERRSPACE_SIZE (50,000 * 10)
620,000      APR_OS_START_CANONERR

    + APR_OS_ERRSPACE_SIZE (50,000)
670,000      APR_OS_START_EAIERR

    + APR_OS_ERRSPACE_SIZE (50,000)
720,000      APR_OS_START_SYSERR