How does Rosa Lee's 0614 song relate to hyperbolas? I don't fathom why this popular Hong Kong mathematics author is discussing hyperbolas and the song lyrics discussed. How do they relate? 

The song is called 0614 by Rosa Lee Ka Yee. My Chinese is too rudimentary, but I'm guessing that the song smacks of relationship and romance and longing for a partner? 

The book is 數。妳。by W. L. LEE. I have pp 49-52 as shown below.
The hyperbola is probably related to a previous song mentioned in the text but not screen-captured.  

The author is trying to talk about songs whose lyrics are related to mathematical concepts.