Not sure what your top set of county numbers means. Does it mean that R turnout exceeds D turnout by X%?
It’s the percentage of 2010 early vote over the 2008 early vote, represented as a formula: (2010 Early Vote)/(2008 Total Vote).
To further clarify, Washington state doesn’t provide breakdown of D or R registration, just the raw early vote totals by county (and not by every county). So, what my number crunching shows is the higher the percentage of 2010 early vote totals in a county, the higher the turnout. And by and large, the counties that McCain won, are turning out bigger percentages of voters over 2008.