A Contract Change Order can modify both the contract (billing-side / Schedule of Values) and the budget (cost-side / estimate) from a single Change Request record — they're separate tabs on the same record. For the concepts behind all this, see Change Order Management.
The grid shows each line's original units, current units, scheduled value, the change you're proposing, and the resulting New Current Units / New Scheduled Value so you can see the effect before approving. It also surfaces other pending and approved changes from separate change orders, so overlapping changes are visible.
Multiple contracts: if a project has more than one Sales Order, a contract filter appears above the grid and lines are grouped by contract. Select a contract before adding a new line.
To help keep unit-price lines complete, the grid watches for a mismatch between a line's dollar change and its units. If a line has a Proposed Changes amount but zero Inc/Dec Units (or units entered with no matching dollar change), those cells turn red so they're easy to spot.
When you click Save with any of these lines still in place, a confirmation appears listing the affected lines, with two options:
This is just a prompt, not a block — it gives you a chance to add the units you meant to enter while still letting an intentional zero through.
Each cost line shows Original Budget, Current Estimate, Actual Costs (with a link to the underlying transactions), Committed Costs (with a link to the open POs), and the resulting New Current Estimate — so you can weigh a proposed change against what's already been spent and committed.
Because Sales Orders aren't natively aware of credit memos, the preferred way to reduce a contract after billing is a negative change order: reduce the contract value with a negative change order, then invoice that amount netted against positive line billings. See Correcting Invoices with Credit Memos for the full picture.