Nanoka says:
... am I supposed to decide what is actually on the map instead of the GM? Same with the tattoo thing.
It is up to you how much you want to decide. We will try to incorporate as much of it as possible, but many things we say can later turn out not to be true.
Nanoka says:
... a Decipher skill roll ..
If you want you can use the roll to suggest how much you get, or even how extraordinary your findings are.
If you can't think of anything, you can roll and will come up with something for you to learn.