Basically, this Act would allow federal agencies to replace only two thirds of the number of employees leaving the federal service until the total federal workforce totals 90 percent of the number of employees as of September 30, 2012. The law expires once that target is achieved or on September 30, 2015, whichever comes first. After that, the Federal Government could presumably go on a hiring binge.
The Act contains provisions where the President can waive the rules if there's a war or a natural disaster or some other unforeseen event.
And, lest you contractors out there think might be a good deal because Agencies will go out and hire contractors to do the work that civil service employees were doing, the Act specifically states that there will be no increase in the procurement of service contracts by reason of the enactment of this Act.
Finally, the Act would require OMB (Office and Management and Budget) to monitor Agency progress and submit quarterly reports to Congress.
There are about 2.2 million civil service employees (give or take, depending upon what source is used). Reducing that number to 90 percent would result in a reduction of 220 thousand jobs.