Think a small error in a cell is a trifle? In 2012, traders at the financial giant JPMorgan Chase suffered losses of $6 billion due to a "copy-paste" error in an Excel spreadsheet. This is not fiction, but a real case that went down in history.
If even world-class experts make such mistakes, what is the probability that a tired manager won't miss a single digit? One wrong formula — and you lose money on every such operation.