But these estimates reflect only some of the debt on the company's properties.
Both estimates reflect a 400 percent increase over 1985.
Officials confirmed today that the lower estimates in the memo reflect the administration's current position.
The new estimate reflects a greater number of reports received by the agency from medical examiners in 32 states for the same two years.
That estimate reflects the last survey of districts about the fees in 2004.
"The reasonable estimates reflect what is the real market."
The lower estimate reflects the book value of the plants, which takes into account their original cost and depreciation.
Christie's is hoping that all three works will break the artists' previous records, as their optimistic estimates reflect.
"The Comptroller's estimate is in line with our projections and reflects the relative strength of the city economy," he said.
The city's estimate of a property's taxable value - its assessment - is limited by state laws and generally does not reflect full market values.