"It is incorrect that the province will spend the reported amount on the official residence," Gauteng Treasury said in a statement.
"What the Gauteng legislature will appropriate for the 2013/14 financial year is R120 000."
Earlier this week Mokonyane's spokesperson Thebe Mohatle told Beeld newspaper that the Gauteng government had spent about R25-million, including the purchase price, on the house since it was bought in 2004.
In addition, R1.2-million of taxpayers' money had been spent on new furniture, linen and curtains for the house.
Asked whether Mokonyane felt it was reasonable to expect taxpayers to pay so much on the upkeep of her home, Mohatle said it was a private matter.
Treasury said during 2012, it was estimated that R400 000 was going to be spent on Mokonyane's residence but only R120 000 was allocated for 2013.
It said the estimate of R7-million was erroneously captured in the Estimates of Capital Expenditure book.
"The correct figure for 2015/16 is R500 000 which is an estimate that will still be subjected to the rigorous processes of Treasury before it is appropriated."
The provincial treasury said corrective measures were currently being implemented in the department to ensure that this did not happen in future.
The DA in the province on Thursday called for Mokonyane's house to be sold.
Spokesperson Jack Bloom said that R13.5-million had been spent on the house since it was bought for R11.5-million in March 2004.
"Why has it cost more to repair than it was bought for?" he asked.
"It should be sold off as soon as possible, with the proceeds used to benefit the people of Gauteng."
Bloom said Gauteng Infrastructure Development MEC Qedani Mahlangu had refused to disclose the names of the companies which refurbished the house when he asked for them in the provincial legislature.
"She has also refused to give details of how they were chosen for this work."
Bloom said he would apply for information under the Promotion of Access to Information Act.
Last year, Bloom approached the public protector to investigate "excessive spending" on Mokonyane's house.