According to a Detroit Free Press report, he and his wife earned a bit more than $400,000 in the year 2015.
During that same year, they donated approximately $95,000 to charities. (This is the sum which went to true charities, i.e., not to professional organizations or political causes.)
By this reckoning, Snyder donated around 25% of his annual income.
For that same year, he paid approximately $31,189 in the form of income taxes. He paid many thousands more in sales tax, property tax, and other taxes.
By far, the greater impact was in the private sector, and this for three reasons: first, the actual dollar amount was greater; second, the private sector charities have lower overhead administrative costs than government programs; third, much government spending is counterproductive, i.e., it exacerbates the very problems it is designed to address.
Private sector charities have a greater, more efficient, and more effective impact than government spending.