Dialing in my Efficiency

Just want to make sure I'm doing this right. I've gone from a consistent 73% to some pretty high %'s

Brew: Mexi Lager
Recipe: 10 Gal

10#Pilsner Malt 1.038
2# Munich 1.035
2# Wheat Malt 1.038
.75# Crystal 60L 1.034
3# Flaked Corn 1.040

So I've been breaking it down like this:
10x38=380 GU
2x35=70 "
2x38=76 "
.75x34=25.5 "
3x40=120 "

For a perfect efficiency world this would = 671.5 TGU (total gravity units)
My pre boil gravity was 1.048 at 12.5 Gal
so my TGU was 48x12.5=600 and taking 600/671.5=.89352
I take it that I'm doing this correctly and my efficiency for this brew was at 89%
Let me know if I'm missing anything. Cheers, Gabe

Your total points was based on 10 gallons but you based your efficiency on 12.5 gallons. What was your final gravity and final volume? If you really ended up at 10 gallons before any losses in the kettle, then yes you are at 89%.

I hit my final volume dead on at 10 gal and my FG was a 1.059 almost 1.060!
Forgot to mention this increase has been due to the fact I recieved a BC malt mill and added direct fire to my MT. +pump.

Your calcs are right, nice efficiency. Makes me want to get a grain mill stat.