I'd like to introduce quite interesting slang of developer in Japan. It is "完全に理解した" Kanzen-ni, Rikai-shita means "Fully understood!".
It is used in the scene that is the very beginning of coding.
Very junior programmer say "Fully understood!" when he finished a tutorial.
Everybody know that he doesn't know anything. But his cognitive bias makes him overconfident. So "Fully understood!" is one of the very humorous slang among Japanese programmer's.
Original tweet is:
"I understand it completely (Fully understood!)."
It means that you have completed the tutorial to use the product.
"I don't know anything."
It means that you have become familiar enough with the product to face its inherent problems.
"I can do it."
Means that you can build the same product from scratch yourself. It can mean that you can make the same product from scratch, or that you are the developer.
This may be known as "Dunning-Kruger effect".