NASHVILLE — Gov. Phil Bredesen said today there is a simple explanation why the number of state employees he needs to accept a voluntary buyout offer jumped nearly 13 percent to 2,277 workers when offers were actually made.

For weeks, the administration had cited a 2,011 figure for employees needed to leave in order to effect some $64 million in annual savings.

Gov. Bredesen said the lower figure was based on estimates of “how many people you would have to buy out at that average salary to get the dollar numbers you needed.

“When they got down and did the detailed work on the thing, they had a slightly higher number presumably because some of the state salaries were on the average lower,” he said.

There “may also be an issue of the mix in federal funding of those employees as well,” he said.

Some employees in areas such as the Department of Transportation and the Department of Labor and Workforce Development have part of their salaries paid with federal dollars.

Employees who have received offers have until Aug. 5 to notify the state they wish to participate in the buyout. If the state does not get enough participants, the reductions could become mandatory in January as the state tries to slash spending because of slower economic growth and flagging revenues.