The way to think about the introvert/extrovert traits is in terms of energy.
An introvert isn't necessarily shy. An introvert is simply energized by solitude, while an extrovert is energized by being around people.
Real life examples.
I have a friend who didn't marry until she was nearly 30. She lived on her own in an apartment, but she had a day job where she worked in a solitary office and almost never dealt with people face to face. She's an extrovert, and it really wore on her. In order to get her energy back up, she needed to be with real, live people.
So she got a roommate.
However, the roommate--an introvert--was an insurance person. She dealt with people all day. By the time she got home at night, all she wanted was to go to her bedroom and be alone.
My friend said she felt lonelier with this roommate than she had when she lived by herself.
My professor who taught the class where we learned about the Kiersey shared this experience. She was a therapist for many years and spent her days interacting with people. She's an introvert. By now you know what she needed when she got home. Quiet. Solitude. Time to lay in the bathtub and contemplate the universe.
Enter her younger sister who wanted to share an apartment. Not just an extrovert, but a flaming extrovert.
Anybody see potential problems?
Professor would come home from work, needing time to rejuvenate. About the time she'd just get her stuff settled, her younger sister would arrive at the apartment after work and blast the radio, sing, talk, and want to chat with Professor.
Guess what Professor wanted to do to younger sister?
What did younger sister do? Not hang around a silent apartment. She hung out with her friends a little longer before coming home. Win/win.
My score balance for the Kiersey for years was 7 extrovert and 3 introvert. As you can see, it's not like people must be all of one or all of the other. As you consider the description of yourself, you should keep that in mind. Someone who is an extrovert with a 9/1 score would view things a bit differently than an extrovert with a score of 6/4.
Does the energy concept make you look at any of your characters differently?