This sets the maximum number of credits this shaper can accumulate, which the description equates to the maximum burst size this channel is allowed to send at its configured peak rate. A larger credit value on this specific shaper lets its channel absorb a bigger burst of back-to-back cells before being throttled back down to its average shaped rate, trading burst tolerance against the risk of that burst overwhelming downstream buffers if set too generously. Raising this from 10 to 100 on a shaper carrying bursty data traffic on this port would let that channel send a much longer run of cells at full peak rate before the shaper starts pacing it back down.