Ok I did my first partial mash today and everything seemed to go fine until the end; I missed my target gravity by a pretty fair amount.

I mashed 4.75 lbs of grain (3lbsMO, 1lbs Crystal 20, and .75 biscuit) with 5.94 qts of water at 154 for 60 mins, batch sparged and came out with 2.35 gallons at a specific gravity of 1.049. This would give me a pretty fair efficiency of about 65.3% (I can post my calculations if necessary).

So here is what I figure 1.049 in 2.35 gallons gives me 1.023 in 5 gallons. In the recipe I am also using 4lbs of Light DME with a potential extract of about 1.044. So I calculated (4*44)/5 = 35.2 which equals another 1.0352 in five gallons.This puts my target OG at 23+35.2 = 58.2GU or 1.0582 am I right? Check my math but the calculations are fairly straight forward. At this point I feel like I am right on track to hit my target OG becuase I assumed an efficiency of about 67.5% so I am not far off. All that's left now is to boil and add the hops and DME, can't really mess that up too much so thats what I did.

Transferred everything to the carboy and to my dismay my measured OG in 5 gallons was only 1.052 (1.051 corrected for 70*F). How could this have happened when all I did was add DME, I did not have any boil overs, and I ended up with exactly 5 gallons. Any ideas what went wrong, am I just missing something here?

Thanks in advance, this beer is going to be amazing either way, and I am enjoying some Apfelwein to ease my concerns,I'm just truly puzzled