A user building a business plan asked ChatGPT to add up a list of twelve numbers for a budget projection. ChatGPT returned $162,161.60 — confident and fast. When the user double-checked with a calculator, the real total was $161,481.60. ChatGPT was off by $680. When asked to re-check its work, ChatGPT wrote out every addition step and returned a different wrong answer: $160,481.60. The AI was confidently wrong, and even self-verification failed. This happened in May 2026, documented by Dre Dyson who was building a real business plan at the time.
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