Undetermined. Could be rolling/wrapping high speed counters. Could be incorrect use of low speed interface metrics. Only way to identify a true root cause is using Detailed Poll Logging via the Data Aggregator dcdebug page (http://DA_Host:8581/dcdebug). Exposing the polled values would lead to identification of root cause.
As speed is used in the utilization calculation, make sure the discovered speed of the interface is correct or if the speed has been overridden with a value that is too low.
Release : 3.7
Component : IM Reporting / Admin / Configuration