Isn’t that the point tho? It’s very confrontational and generalizing to say “your numbers are always wrong”. Instead, even if it’s a recurring pattern, stick to hard facts and actual examples you can point to. If there has been a history of issues, the person will identify that pattern themselves, unless they’re a complete idiot. And if they fail to identify that, the next hard conversation to have is “you aren’t excelling here and it’s time for a change”.