It's informal for "totally kidding" which can also be considered informal.
The use of "totes" is due to the fact that many teenage girls usually say "totally" in their daily interactions with intimate people, hence the adoption of "totes" in the speech. Although an informality that many would call "innapropriate", "silly", others argue that it's time saving due to how fast the conversation flows.
It's informal for "totally kidding" which can also be considered informal.
The use of "totes" is due to the fact that many teenage girls usually say "totally" in their daily interactions with intimate people, hence the adoption of "totes" in the speech. Although an informality that many would call "innapropriate", "silly", others argue that it's time saving due to how fast the conversation flows.
e.g: "somebody missed our house meeting today"
" I'm sorry, I...
"Totes kidding, I knew you were busy, don't worry"