Understanding composer and database problem

[Sung Jun Hwang]

Has anyone understood the following instruction on composer and database assignment?

// The default ranking is 10 which is the lowest possible. 

// Notice we use const in C++ instead of #define. const int kDefaultRanking = 10 

It says 10 is the lowest possible ranking yet in the last instruction for making error proof database:

a ranking should always be in the range 1-10. 

I do not follow what the ranking range should be and if we can promote/demote if it is over or below the range.