Transcription is when mRNA is formed on top of DNA.
If you had a sequence like this one:
TTCACG
It would end up inverted (C switches with G, and A with T).
AAGTCG
The only thing is, RNA uses uracil (U) instead of thymine (T), so our mRNA would look more like this:
AAGUGC
Now let's compare this to the transcription we're given.
AAGGC
What's the difference? Well, it looks like that U has been deleted.