Efficiency question

I've been struggling with efficiency with my brewing.  I've been making some changes but don't understand the results I'm seeing in BS3.  For the attached brew, I had 81% mash efficiency but only 58% BH efficiency.  I did some math and wonder if BH shouldn't be 70%.
pre-boil was 6.4G x 46 pts (294)
post boil was 5.25G x 49 points (257) (I did a shortened boil adjusted in equip profile)
The 257  is 87% of the sugar into the boil.

I then multiplied the BS reported mash eff. (81%) with the 87% boil to get 70%.
I assume I'm doing this wrong. How do I get to 58%?

Thanks & Happy 4th!

\\Greg

If I am looking at your recipe correctly, your post mash gravity reading is including the sugar addition which was made at the beginning of the boil (?).  This throws off the BeerSmith calculation of mash efficiency which you are using to base your calculations.  If you took a gravity reading before the sugar addition, you probably came up with a gravity of around 1.038.  This would put your actual mash efficiency at 67%.

To expand on what Oginme is saying; Post Mash gravity is the gravity of the wort right out of the mash tun. Pre Boil gravity is the gravity of the mash plus the sugar additions you added. You may have entered the pre boil numbers into the post mash field.