10X6 has a 5 inch radius. Pi X R X R =78.5 sq. inches of disk area .

12X6 has a 6 inch radius..................=113 sq. inches of disk area.

Comparing the disk area of the 10x6 to the disk area of the 12X6 78.5 / 113 = 70 %

Comapraing the displacement of the 0.46 to the dispalcement of the 61 46/61 =75 %

Seems to add up.