If someone is described as "good at something", in your opinion how good is that person at this activity?

Both professional activities and hobbies

For example... If a new hire is introduced as "good at Python and C++" at work, what does this imply about the person's skill level in your opinion? Or if someone says they are a "good runner", what would come to your mind? Or is it field-dependent?

Asking because sometimes I'm not sure if I am under/over-exaggerating my own abilities when meeting new ppl at work/etc....