我知道你长短我知道你深浅
[wŏ zhī dào nĭ zhăng duăn wŏ zhī dào nĭ shēn qiăn]
This username suggests that the person knows someone else's strengths, weaknesses, and true nature thoroughly. It conveys a sense of profound understanding or familiarity with another person, often used to imply a deep bond.