How should a builder’s change-order markup be defined?

A percentage markup on an owner-requested change can mean more than a fee on added labor and materials. It may also be applied to design revisions, subcontractor charges, or costs tied to rescheduling, and the contract may set a minimum charge even for a small change.

What wording have you found useful for defining which costs the markup covers and whether that minimum applies? I’m also curious how builders calculate credits when the change deletes work, so proposals can be compared on the same basis rather than looking only at the percentage.