I had a similar experience with my wife's I-797 having her name misspelt and it was misspelt in the petition itself. Our attorney informed USCIS and they told it will take 7 days to pull out the file. Later they updated the status in their website from "Decision" to "Acceptance" with notes as you wrote. And still the website shows the same status. However, our attorney received the amended I-797 last week or before (she told us on this Monday that she already received it, did not mention the date). The whole thing might have took around 4 weeks.
I believe your attorney will receive the amended notice within a week's time.