The idiom ‘got your number’ means that someone understands you very well, especially in terms of your character or behavior. It can also imply that a person knows your weaknesses or has insight into your true motives.
For example, if a friend says, ‘I know you’re just pretending to be happy, I’ve got your number,’ they are expressing that they see through the facade and understand the real emotions behind it.
This phrase can be used in a variety of contexts, often with a tone of familiarity or even manipulation. It suggests that one person has a level of insight into another person’s thoughts or actions that most people might not possess.