This read-create integer sets the Committed Burst Size (CBS) for queue 1, with 0 indicating the burst-size shaping is not active. CBS defines how large a momentary burst of traffic queue 1 can send above its committed rate before shaping kicks in, which matters for accommodating bursty applications without over-relaxing the rate limit. For example, an admin shaping queue 1 to a small CIR but a generous CBS would let short bursts of traffic through without immediately throttling them.