Partial Mash Efficiency

So I recently started developing my own extract/partial mash recipes with the use of BeerSmith and brewed my first, a Hefeweizen, yesterday. The recipe was as follows:

5 lbs. Wheat LME
1.6 lbs. 2 Row Pils
0.25 lbs. Crystal 20
1 oz Hallertauer
Wy 3068

Beersmith showed that all my measurements were in the clear for the style and I was pretty happy with how it was shaping up, so I went and brewed it. Now, I wasn't too sure as to how to input my efficiency in Beersmith considering 73% of my brew was 100% efficient so I looked around and figured I could get away with 65% considering I sparge my grains pretty well.

This recipe was supposed to yield an OG of 1.45 at that efficiency in a 5 gallon partial match brew. Unfortunately what I ended up with was more like 1.36. Is this a question of the wrong efficiency or did I do something else seriously wrong? The boil was 3 gallons and I lost maybe .2 gallons of it by the end of the boil.

If you used top-off water the problem is most likely that the concentrated wort didn't mix well with the water and that has thrown your hydrometer reading off. Don't worry too much about it, at this point there isn't a lot you can do for it.

For your partial mash you need water the correct temperature and the grains to be well crushed. If you had that, your partial mash would have yielded about what was predicted.