Hi. i need help on determining my actual efficiency. I estimated my efficiency at a higher number when building by recipe and have re-adjusted them since but now I'm confused.

here are all my numbers

my mash thickness ratio was about 1.3qt/lb, mashed for 60min about 155F

original estimated OG (at 70%) was 1.082 and my actual OG was 1.070. according to my efficiency calculations i should have been at 1.060 (50.4%)

had i had 15.5lbs of grain and sugar, 5gal of wort collected, my preboil og was 1.0568

here was my equation= (18.925L)*(1.070gravity)*(.175plato as a decimal)= 3.5437 then i divided by my total weight was 3.5437/7.03068= .5040 or 50.4%.

my question how is how is actual og higher than the adjusted og? Shouldn't my efficiency be closer 64%?

i do batch sparge, if that makes any difference.

Me and math are not friends so i could be missing something, so any suggestion or edits are welcome

thanks