Signed integer indicating the precision of the system clock,
in seconds to the nearest power of two. The value is rounded
to the next larger power of two; for instance, a 50-Hz(20 ms)
or 60-Hz (16.67 ms) power-frequency clock would be assigned
the value -5 (31.25 ms), while a 1000-Hz (1 ms) crystal-controlled
clock would be assigned the value -9 (1.95 ms).