EXFO FTB-800 Series for FTB-1 - Manual (Page 341)

Test Results
NetBlazer 331
Service Performance
Note: Delay variation measurements smaller than 15 μs will be discarded, not
used for the sampling process, and “< 0.015” is displayed as the minimum
value. For the Current value, Not measurable is displayed when no delay
has been measured in the last second.
Errors

Frame Loss indicates that a sequence number is missing in the
received frames. The pass/fail verdict when enabled reports only the
verdict when it is fail. Seconds, Count, and Rate values are reported.

Out-of-Sequence indicates that the received frame sequence number
is either smaller than the expected frame sequence number or is a
duplicate number. The Out-Of-Sequence will not be considered in the
global verdict. Seconds, Count, and Rate values are reported.
RX Frame Count
The RX Frame Count indicates the number of frames received matching
the selected service ID.