Dinky’s assignment is to describe somepony who she believes she knows very well using 500 words or less.  That pony will also have to write a description of themselves in 500 words or less.  

The point of the exercise is to help the young fillies and colts think about the ponies in their live and to encourage them to share what it is that they feel makes somepony special.  

Having chosen to write about her mother Dinky borrows her mother’s unused words to try and describe her and ends up learning something in the process.