Trying to calculate my efficiency correctly

I can see that your post mash and post boil gravities are really off.

For example you state an estimated post mash gravity 1.037 after correction, but then have 1.030 post boil. This would only be possible if you diluted with water. Post boil will always be higher from the boil off evaporation.

In any case, I think the hydrometer calculator is setting you in a wrong direction by it being too far of a temp spread, and you really didn't have 1.037. All hydrometers are different, and have their own temperature correction but only are accurate if you're within their tolerance usually +- 10°F or so.

It's best to cool a gravity sample to within tolerance then take a reading and adjust based on your hydrometers specific instructions. Refractometers are useful as an alternative.

Only a couple efficiencies matter. Mash and brewhouse. Mash is the big one, and where you get your fermentables so dialing this in helps a lot. Brewhouse is basically everything combining mash efficiency with end volume of beer. With the ultimate goal of buying exactly the amount of grain needed for X gallons and product and get the desired ABV.

Post mash/Pre boil and post boil reading are useful to hit numbers, Gravity correction calculators help with adjucts like DME to raise SG or water to lower SG. An alternative to adding adjuncts to raise SG is to boil off more at the sacrifice of volume, but take care hop times need adjusted too.

Also you have about 4 liters of over sparge there which will reduce your mash efficiency. Recipe calls for 20 strike, 10 sparge. For 26 pre boil.

1.030 post boil is really bad for that recipe. Check and make sure all your grain was milled and the wheat was flaked.

First, I can't see your images from my work computer so I'll explain it from scratch.

Each type of grain (base malt and adjuncts) have a potential yield of sugar. For simplicity's sake, we'll use the "point system" (that is Specific Gravity minus 1 times 1000), so for a Specific Gravity of, say, 1.040, we would say that you have 40 point (1.040-1 = .040, .040 * 1000 = 40).

Brewing software, such as BeerSmith or Brew Target have the potential points built in (it's also available from the manufacturer and often on the bag). US 2 Row has a potential of 36 points (if you had 100% efficiently, and put 5 pounds in a 5 gallon batch, you'd have a measured SP of 1.036).

You're going to measure your gravity at the end of the boil (hops don't add a lot to this). So, Efficiency = Measured Gravity Points / Potential Gravity Points. Let's take this a step further though because sometimes we don't always boil off what we want.

Efficiency = (Measured Gravity Points * Actual volume)/(Potential Gravity Points * Target Volume).

FWIW, Brad Smith does an excellent job of explaining this here.

Looks like you are doing it right to me, using those calculators.

The only thing that might change your actual # is the calibration temp of your hydrometer. Be sure that it is 20C. Some hydrometers are closer to 15 or 18C, depends on the manufacturer. Although that won't change your OG much.

67% mash efficiency does seem like a normal for BIAB.

If the gravity is to high preboil, you can always do a calculation of how much sugar you have and dilute the boil with water. In the end, you'll just be leaving more wort behind to still hit the same batch size. If the gravity is to low preboil, you can try and squeeze your grain bag some more, sparge with a little water or do a calculation and add a little dry extract to compensate.

Your OG seems low, but based on the recipe it makes sense. As long as you were trying to make a low gravity beer it seems like you are on track.