The %FrontWindowFrame% token returns the frame of the front window (same as %WindowFrame%1%).
The returned array resembles this:
228,23,1314,1173
x1,y1,x2,y2 228 == x1 23 == y1 1314 == x2 1173 == y2 x1,y1 refers to the upper left corner of the window. x2,y2 refers to the lower right corner of the window.