The proofread reads every line of the edition's manuscript and suggests fixes for real mistakes only: spelling, typos, grammar, punctuation, missing words and inconsistent typography. Your style and word choices stay yours.
Each suggestion shows the line before and after, with the reason. Accept or reject each one, then apply the ones you accepted: they make a new version of the manuscript, and the next builds use it. It costs $0.10 per 1,000 words of Studio credit.