Post Boil Gravity v.s. Original Gravity

[The Boreal Brewing Company]

What is the difference between these two?

This is saying the Post Boil gravity is 1.069 but the OG is 1.074. I'm not sure why these are different? are they not temperature corrected? Thanks.

 

[Craigerrr]

There are a few other threads below discussing this very thing, maybe skim through those to get your answer.