In NAVdisplay, one of the measurements available in the NCOM output from an RT is "CAN last error code". When displayed in NAVsuite 2.7 (the version current at the time of writing) and earlier versions, it is repeated, so the code 64 appears as 6464.
The number represents a combination of individual flags. Let the code in binary be HGFEDCBA where:
A (1) CanErrorFlagStuffing - Too many equal bits in a received message have occurred.
B (2) CanErrorFlagFormat - A fixed format part of received frame has the wrong format.
C (4) CanErrorFlagAcknowledge - A transmitted message was not acknowledged by another node.
D (8) CanErrorFlagBit1 - Bus was dominant (0) when wanting to send a recessive level (1).
E (16) CanErrorFlagBit0 - Bus was recessive (1) when wanting to send a dominant level (0).
F (32) CanErrorFlagCheckSum - The CRC check sum was incorrect in the message received.
G (64) CanErrorFlagBusOff - The CAN controller is in bus off state.
H (128) CanErrorFlagNotActive - The CAN driver is not active.
The code is the sum of all flags set, so 193 in binary equals 11000001 meaning that H, G, and A are set.