This cyclic counter tallies received token ring frames whose 'A' and 'C' bits were 1 and 0 respectively, meaning a destination station recognized the address but did not copy the frame -- typically because it lacked buffer space. Admins watch it as a sign of a receive-buffer-starved station on the ring dropping frames intended for it. For example, a client device reporting missed data with a rising A=1/C=0 count would point to that device running low on receive buffers.