To the original questions:
What would you do in this situation?
Drop the ten and pick up the $4 because I'd feel I was hogging the table in a busy restaurant. (And I'd feel the same if one was hogging a table in a busy restaurant milling about after a meal.)

What is normal, correct, whatever you want to call it? Is $4 acceptable?
Anything is correct and yes, $4 is acceptable. I go by the philosophy that there really aren't any rules to tipping, just guidelines.

Background: Yes, I did serve for a while but years ago.