Variance at Completion (VAC)
Variance at Completion (VAC) is the difference between the Budget at Completion (BAC) and the Estimate at Completion (EAC) (VAC = BAC - EAC). It may be calculated at any level from the control account up to the total contract. It represents the amount of predicted overrun (negative VAC) or underrun (positive VAC).
DoD Earned Value Management System Interpretation Guide (EVMSIG)
The Variance at Completion (VAC) is computed by subtracting the Estimate at Completion (EAC) from the corresponding Budget at Completion (BAC). A negative variance at completion is unfavorable indicating the contractor is forecasting an overrun. A positive variance at completion is favorable indicating a forecast of a contract underrun.
A plain language definition for a negative $10K variance at completion is the contractor is forecasting a ten thousand dollar cost overrun at completion.