At my previous company I was in a board meeting where I got asked a question about my own business and my answer had adjectives (“lots”, “tons”, etc) not numbers, when it should have had numbers. My board member Alfred Lin, the former COO at Zappos (sold to Amazon for $1B) said to me (paraphrased, after all these years I don’t remember it word for word):
Let me tell you what knowing your numbers looks like. One time during a Zappos board meeting some analyst brought in a laptop and was presenting to the board. He got to a slide with our detailed P&L from the last few months on it. I immediately spoke up and said something's wrong with your presentation, those numbers are not right.
Flustered, he looked at his PowerPoint and realized that somehow his linked spreadsheet got messed up. He tried to fix it right there, and here we all are, the entire board sitting there watching him sweat as he tried to fix the linked spreadsheet.
After few seconds I stood up got to the whiteboard and hand wrote our entire P&L, row by row, column by column, on the whiteboard from memory. I told the board that we should just use these numbers and continue moving forward with our discussion. So we continue the discussion on my whiteboard handwritten P&L numbers and finally many minutes later when the analyst finally fixed his spreadsheet and triumphantly projected the correct spreadsheet onto the screen… they were the same as the ones I had written down on the whiteboard.