The further 10,000 cases were left out of Sunday and Monday's results due to a data processing issue.
"These positive RATs from Sunday and Monday artificially inflate the cases being reported for the 24 hours to 4pm Tuesday," NSW Health said in a statement.
"The data processing issue, which has now been resolved, is only affected reporting of cases. All of these cases were still connected to clinical care as per normal processes with positive Covid-19 results."
Case numbers have doubled in just 24 hours after NSW recorded 10,689 infections on Tuesday.
Last week Health Minister Brad Hazzard revealed cases were expected to spike as a result of BA. 2.
New South Wales Health Minister Brad Hazzard looks at NSW Premier Dominic Perrottet. Photo / Getty Images
Across the world, many countries have experienced a surge in cases due to BA. 2, with the Statens Serum Institut issuing a warning about two weeks ago.
"BA. 2 is gaining ground in many places worldwide," the Danish research institute said.