This Counter32 is a running total of frames received over this virtual circuit since it was created. An admin checks it alongside csFrCircuitSentFrames to see whether traffic on a DLCI is balanced or heavily one-directional, which can hint at a misbehaving application or a one-way connectivity problem. For example, a VC showing steady sent frames but near-zero received frames would point the admin toward a fault on the remote end rather than the local interface.