First All-grain BIAB - overshot gravity

I am in the middle of my first attempt at all-grain brewing. I'm using the Dry Dock SS Minnow Mild kit from Northern Brewer's Pro Series. It is a total of 7.2 lbs. of grains, which pushed the limits of what my strainer could hold on top of my kettle as it was draining and as I did the sparge.

I took a preliminary gravity reading before the boil started. According to Brewpal, at the 4.25 gallon volume my boil started at, I should have gotten 1.045 as my gravity. I actually measured 1.062 (temp corrected). Apparently, my efficiency was better than Northern Brewer calculated for.

Here's my question:
How much extra water should I add (beyond the 5 gallon target volume) in order to get to my 1.037 target OG? After I chill it and top it up to 5 gallons, I'll take another gravity reading before making any final decision to add more water. But I just wanted to throw this question out there before I get to that point.

I'm using a 6.5 gallon carboy, so there is a little room for evening things out before I get nervous about having enough headspace.

Nope - something simply doesn't add up. I do 5 gallon batches and my efficiency is in the low 80's. It takes an 11 to 12 lb grainbill to get into the 1.060 range. Your hydrometer might be off or perhaps you measured in an area that had a higher concentration of sugar than the overall average. I would only expect something maybe in the 1.040 range.

Maybe someone else will weigh in on this...

It was the partial volume reading that was so high. When I topped it off at 5 gallons it was still a few points high. I added a little bit of water, and got it to 1.039 (still higher than the 1.037 target gravity) and decided that was close enough.

Chilled it down to 60 F and pitched the yeast. It's bubbling away and has risen up to about 63/64 F, so far this morning.

This being my first all-grain, it was interesting to me that the bubbles from my aerating/shaking the carboy didn't fall off at all before being pushed aside by the bubbles from the fermenting. I'm wondering if that means this batch will have some serious head retention.

Oh yeah, and there is a ridiculous amount of cold break material at the bottom of my carboy. I guess that might be an all-grain thing.

its a BIAB all grain thing