我只知道我爱你如此而已
[wŏ zhĭ zhī dào wŏ ài nĭ rú cĭ ér yĭ]
It directly means 'All I Know Is That I Love You Just That Much'. This phrase shows the extent of the speaker's devotion without needing anything more than love to describe their feelings towards another person. Such a user name implies strong emotional connection and commitment.