This sets how many consecutive cells this circuit is allowed to send at its full peak rate before the switch expects it to drop back toward the sustainable rate, effectively defining the size of tolerated traffic bursts for this VBR circuit. An admin tuning a circuit for bursty application traffic, like periodic large file transfers, would increase cktAtmMBS to accommodate those bursts without triggering cell tagging, while a circuit expected to have smooth, steady traffic would keep this value low. For example, setting cktAtmMBS to 50 lets this circuit send up to 50 consecutive cells at its full peak rate for each burst before the traffic contract expects it to settle back to the sustainable rate.