Highway gears is one thing, but this???

I have an 8 1/4 rearend under my 68 barracuda. I did the old "jack it up and turn the tire" to get my gear ratio.
This is how I did it:
Jacked up both rear tires. (I have suregrip)
Chalked my tire and the floor.
Made 2 full turns of my tire.
Counted the 1/4 rotations of my drive shaft by watching the caps on my u-joint.
I counted 25.25 1/4 turns.
25.25/4=6.3125 ratio

So, did I do something wrong or do I just have really high gears?