This Counter64 field tallies the bytes on the reverse direction of this bidirectional CES tunnel that were dropped on ingress, specifically traffic that the policer discarded outright on ingress because it exceeded even the excess-rate allowance. Because this is the currently open, still-accumulating measurement interval that keeps climbing until its boundary is reached and it rolls off into the history table, any nonzero, growing count here is real traffic loss the attached service is experiencing in that direction, not just a policy flag, and tracking it separately per direction (forward vs. reverse) lets you tell whether a problem is one-sided rather than affecting the whole tunnel. For instance, over the in-progress 15-minute bin this counter might climb by roughly 2 KB of reverse-direction traffic — if the matching counter for the forward direction stays far lower (or far higher) than this one, that directional imbalance is itself the diagnostic clue, since a healthy bidirectional tunnel would normally carry fairly similar dropped volume both ways.