60-month backlog at December 31, 2007, will be reduced by approximately $22 million; and 12-month backlog entering calendar year 2007 was reduced between $3 million and $4 million, which reduces both our revenue and operating free cash flow by the same amount, and results in a reduction in our GAAP and adjusted non-GAAP earnings per share guidance of approximately $0.06. The impact of higher expenses related to our review of historical stock option granting practices. Our previous guidance assumed total expenses from this review of approximately $6 million. Due to the length of the review, our new estimate of expenses for the review is approximately $7 million. This expense impacts the quarters ending December 31, 2006 and March 31, 2007 by approximately $3 million each, and the quarter ending June 30, 2007 by approximately $1 million.
Incremental compensation expense between $1 million and $2 million primarily related to a post-employment agreement with a former executive officer. We now expect our revenue in the second half of calendar year 2007 to be approximately 20 to 25 percent higher than in the first half of the year. In addition, we expect our reported GAAP expenses in the second half of calendar year 2007 to be approximately one to two percent higher than in the first half of the year.
Based on the specific items noted above, our adjusted financial guidance for calendar year 2007 calculates as follows:
Operating free cash flow between $57 million and $67 million; Revenue between $428 million and $447 million; 60-month backlog on December 31, 2007 between $1.309 billion and $1.339 billion; GAAP earnings per share between $1.05 and $1.34; and Adjusted non-GAAP earnings per share between $1.51 and $1.80. March Quarter Operating Highlights
"We had solid contracting and strong cash generation in the March quarter," added Heasley. "We continue to see the need for major financial institutions, retailers and payment processors to replace or update their legacy payment infrastructures in the face of ongoing regulatory pressures, ever-increasing electronic payment volumes and the costs and complexity of supporting older technologies."
We signed a major wholesale payments deal in Europe with a top 20 world bank, who licensed our ACI Money Transfer System to help them upgrade their global payments infrastructure and comply with the impending SEPA regulations. We signed new BASE24-eps deals with two of the top ten banks in France, our first retail payment engine deals in France in many years. We signed a top U.S. bank to run our ACI Enterprise Banker product in a hosted model, validation that our ACI On Demand initiative has interest within the banking community. We signed several deals in the quarter with financial institutions in the United Kingdom to help them meet the new requirements for the U.K.-based Faster Payments initiative. In addition to the contracts we signed in France, we signed several significant BASE24-eps deals across our geographic channels, with both new and existing accounts, and on a range of operating platforms. Overall, we signed thirteen new accounts, licensed twenty-five new applications with existing customers and we signed 28 capacity upgrade licenses over $100 thousand.