What was my mash efficiency?

Hello all!

So, just mad the plunge into AG equipment over Christmas and brewed the first batch last week. Been racking my brain trying to figure out what my mash efficiency was. Here's the breakdown:
11lbs 2-row pale
1lb caramel 40
Target post-boil OG of 1.066
Actual post-boil OG of 1.058
After 10 days in primary, checked gravity and I'm at 1.009. I have hit the predicted ABV of 6.5%, despite the predicted FG of 1.017 (based on the predicted 1.066 OG)

I know I should have sparged longer than my 10 minutes.

What the heck was my mash efficiency?

All help, heckling, and advice welcome.

It looks to be about 69% efficiency. Well a 6.33% is close enough I really don't think you'll notice the .2%.

This is great for brewhouse efficiency: http://www.brewersfriend.com/brewhouse-efficiency/

Did your mash temps drop too much to get such a low FG?

My target mash temp was 153 and I hit it. Was still 153 after the 60 minute mash.

The only thing I can think that made a huge difference was the amazing 85% attenuation of the yeast. 2 packets of rehydrated safale us05.

Also, @tennesseean_87, brewhouse efficiency is different from mash efficiency, no?

And on the "wort collected" box on that calculator, is that pre-boil or post?

I'd need to know the size of your batch. What makes you think your ABV is 6.5%? If that is a 5 gallon batch, your efficiency is somewhere around: (58/((11X37 + 1X35)/5))X100= 64.6%. You can go to hopville.com and plug in grain quantities and play around with the efficiency until your OG matches theirs.