What am I missing?

How is it possible that my pre boil gravity and post boil gravity are the same? I collected 7 gallons of wort and took a sample that I cooled and measured the gravity at 1.054. Then my OG before pitching with 5.25 gallons of wort in my fermenter was 1.055. I let the pre boil sample cool outside in an open container, would this have anything to do with it? Am I reading the hydrometer wrong? I would expect an OG of 1.068 or so with that pre boil reading. What gives? Thanks in advance for any help, this is my 2nd all grain and I'm still trying to figure out the science behind all this.

It could be the case that the wort you collected wasn't mixed in well. Also, you could have had bubbles forming on the bottom of the hydrometer (this is why you're supposed to give the hydro a swirl). Can you take another reading?

Was the temperature for both measurements the same?

Yeah, you gotta stir the bejeezus out of your wort before taking a sample - I've had skewed readings three times because of this. Even worse is that I realized what I did wrong the first time it happened so I always try to thoroughly mix the wort, but despite this I've had problems with it two more times.

You also need to normalize every single hydrometer reading you take based on its temperature.

Thanks for the ideas. The temps were a little different, but I adjusted for it with the pre boil gravity. Maybe the stirring got me. I figured the wort, when transferred/ siphoned to fermenter was mixed enough, but maybe not. Should I be taking a first running gravity as well as a pre boil gravity? This is just my 2nd all grain, but the first came out great and hopefully this one will as well. Hopefully it's just user error on my part with the hydrometer and not mixing enough. Thanks again for the help.