25% growth in our current economic situation would be a highly optomistic estimate. Last year it was one percent (in the third quarter of 2011, latest available info, it was growing at an annual rate of 1.8%
http://www.tradingeconomics.com/united-states/gdp-growth ). As a percent of GDP they are also projected to rise which means that not all of the revenue growth comes from economic growth (going from 15.3% of GDP to 15.9% of GDP).
Compared to 2010, he reduces spending by $700 billion or so right off the bat and lets it rise slightly each year after that. The remainder of the gap is closed by higher tax revenues. (2010 total outlays were $3.5t and in Ron's first year outlays are $2.8 trillion).
Give him credit though- nobody else is willing to provide any details on how they would reduce the size of government beyond some vague phrases and calling for a Balanced Budget Amendment or blaming somebody else like the other party.