Omnitik ether1 RX/TX too-long ??

Omnitik reports at ether1 (Overall Stats) rx/tx too-long?
This port is configured as MPLS interface (mpls MTU 1524) and max L2MTU is 4076, curent L2MTU 1600.

Latest RoS ver.

Any suggestions?
What is main meaning off that report?