You know what? I think that Cirno's explanations are indeed confusing, he was able to confuse his own co-host, myself! So I think I should help you because I know what's the point of it now.
A mnemonic is taking the first letter of a list, need to complete a word for the following... as far as I know, it is with...
D
E
G
R
S
G
C
I think that Cirno haven't exactly explained the objective or even executed it well... hmph.
I'm seeing some people are really confused about this objective and I hope this clears things.