Commission is the barn's cut for selling the livestock. It's calculated from the commission rate in effect for the sale (stored in basis points) applied to the gross, and may be bounded by per-head minimums and maximums from the fee schedule. This is the largest deduction on most settlements. The field is read-only — it's computed during the settlement run from the sale's fee snapshot, not entered by hand.
A consignor can have a negotiated rate that overrides the standard one. The rate that actually applied is captured when the settlement runs, so later fee-schedule edits don't change a finalized settlement.