Variance Amount Calculation in Budget Inquiry-Accounting

Hello,

Does anyone here know how the "variance amount" field is computed in the Budget Inquiry-Accounting display?  I am showing small encumberances of less than $1.00 when comparing the "Actual Amount" to the "Variance Amount".  I have verified all of the costs for purchase orders on the job for the affected cost type, and I can verify the "Actual Amount" but the "Variance Amount" I cannot determine.

If more information is needed please let me know.

Matthew