Depending on the monitored device and OID, statistical information can be derived from 32-bit counters. These counters offer a maximum value of 2 to the 32nd power (4,294,967,296). You can decide how Toolset Network Performance Monitor compensates when a 32-bit counter reaches maximum capacity and rolls over to zero. The default method detects a counter rollover and ignores the zero value. Instead, a new sample is scheduled in 20 seconds. This method can cause slightly skewed total bytes transferred numbers.
The more advanced method, which produces skewed numbers when manual counter resets occur, detects a counter rollover and uses the following calculation to correct for the rollover to zero:
currentValue + (maximumCounterValue - lastCounterValue)
If manual counter resets are rare, this method produces the most accurate results.