NTP Jitter & Offset

Values are offset +20 microseconds because MRTG can't render negative values in a graph. So the true 0 mark is the center of the graph.

The time difference between two clocks, relative to a selected reference clock. Represents the amount to adjust the local clock to bring it into correspondence with the reference clock. Offset is a temperature-affected, as temperature affects the quartz oscillator.
The estimated time error of the system clock measured as an exponential average of RMS time differences. Limited by the Precision of the clock
How precisely Stability and Accuracy can be maintained within a particular timekeeping system. Another way of thinking of this, is as the smallest unit of time a clock that can be read from the clock. This is a number indicating the precision of the various clocks, in seconds 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). The clock in the Raspberry Pi has a precision of -19 (0.000001907s, or about 2 microseconds).