Opening the book…
Warmth without a stated standard reads as permission. People walk out of a gentle conversation genuinely unsure whether the work was acceptable, and they repeat it. Naming the bar in the same moment lets both things be true: you are on their side and the work was not good enough.
Say the specific thing that was missing and what it needed to be, then say you expect they can get there. "This went out with three numbers that didn't reconcile; it needs to reconcile before it leaves your hands. I know you know how." Don't split it into a kind meeting now and a standards meeting later — the second one never lands.
When someone already knows exactly how badly it went and is visibly wrecked, restating the bar is piling on; steady them first and set the standard the next day. Skip it too when the miss was caused by a system you own rather than their work.