Help with ProMash efficiency calc


Yesterday I brewed a PM recipe that used 7 lbs of grain and 2 lbs of DME. I've never had stellar efficiencies  typically about 65%  but based on yesterday's results I wonder if I've been using ProMash correctly.
At 65% and 5.0 gal batch size ProMash predicted 33 points from the mash and 18 from the DME, target gravity of 1.051.
I hit an OG of 1.050 but had a final volume of about 5.3 gal so I understand that if I were to boil longer, I'd have a higher OG. But what I don't get is ProMash said that I got 40 pts from my mash and calculated my efficiency at 78%. But if I got 40 pts from the mash then that means I only got 10 pts from the DME and extract should always be 100%. So what gives?
SP
