Missed OG

Well, my 4th batch is in the fermenter, but I missed my OG horribly. I'm sure it will still be good beer, but...
The particulars:
Strong Scotch Ale (Wee Heavy) extract kit from Brewmasters Warehouse
Full Boil (6.25 gallons)
Steeping grains: 8 oz. Medium Crystal
8 oz. Gambrinus Honey Malt
4 oz. Extra Dark Crystal
4 oz. Crisp Pale Chocolate Malt
3.3 lbs Extra Light LME
3.3 lbs Amber LME
2.0 lbs Extra Light DME
1.5 oz Kent Goldings (4.5% AA) @ 60 min.
0.5 oz Kent Goldings (4.5% AA) @ 5 min.

1st I steeped small using 2 quarts of water. My temps were all over the place never above 170 and never below 145, but very much out of control. The water just barely covered the grains. After 30 minutes I rinsed the grains with hot tap water (about 1 quart) and added this to my boil kettle and brought total volume up to 6.25 gallons. Added 1 can of LME at start of boil along with the bittering hops.
At 20 minutes I added the 2nd can of LME, all of the DME, 1 whirlfloc tablet and my IC. At 5 minutes I added the last of the hops. Cooled the wort to 64 deg F, aerated, and pitched dry Nottingham yeast.
The target OG was 1.080, I got 1.058 (unadjusted for temp). Any ideas where I went bad? Final volume of wort was 6 gallons into the fermenter.

I'm not an expert on extract brewing, but here's the numbers I came up with.

1.5 lbs steeping grains @ 30 points per pound = 45 gravity points (this might be generous)
6.6 lbs LME @ 34 points per pound = 224.4 points
2 lbs DME @ 45 points/ lb = 90 points

Total of 359.4 gravity points / 6 gallons = 59.9

I put your target OG at 1.060.

Maybe I'm way off on my potentials or math, but it looks like you just didn't use enough extract.

Hopefully someone can prove me wrong...

Thanks jmick. I looked at some online calculators and played around with them trying different combinations. If I had boiled down to 5 gallons from 6 I would have been around 1.070. I thought I may not have had enough extract, but I followed the kit instructions and there was nothing missing from the list of ingredients. Would taking the OG sample at the same time as using an air stone make any difference?

Yeah I think you took a recipe for a 5 gallon batch, and diluted it to 6 gallons.

I don't think aeration would have affected gravity readings

Wish I had thought of that before I pitched the yeast!

I guess now I have a Wee Light instead of a Wee Heavy!

Yep, I got 1.066 for your OG in BeerSmith. You could always boil up another 2-3lbs of DME (in as little water as possible), cool and add to the fermenter.

How little water are we talking about? 1 cup per lb?
How long do I boil?
Mix as I add or try not to disturb too much?
Thanks for all the help!

I'd try just 2 cups of water and go from there, if you need more to dissolve the DME then add more and boil then cool.

Boil for 20mins to remove all the O2 from the water and to sanitize it.

DO NOT MIX, be very gentle in adding the new wort to the fermenter.

Thanks, I'll be leaving work early today to try this!