A struct used to report statistical metrics data for a GenServer process.

The fields are:

• callbacks - the total number of callbacks handled by the process

• total - the total time spent (µs) on all callbacks

• max - the maximum time spent (µs) on any callback

• min - the minimum time spent (µs) on any callback

• mean - the mean time spent (µs) on any callback

• stdev - the standard deviation around the mean time spent (µs) on any callback

• range - the difference between max and min time spent (µs) on all callbacks