After you file

I am not filing as a joint, I am just a little confused. I filed today, but turbotax wanted my 2018 AGI. I worked for my grandpa in 2018 and his tax agent amended me, and my taxes that I owed in 2018 were taken care of. I am just kind of worrying that if I enter my official AGI, some irreversible mistake will ensue and I'll owe money from 2018 that was already paid. If that makes sense, please let me know what I should enter in my AGI. I filed a 1099 form by the way