When you setup a spreadsheet, you choose a column or cell to show the NPV. You use the npv formula on this cell and apply it to inputs from other columns or cells.

This process of deciding what data to put in what column and how to apply NPV to it is non-deterministic. You could choose to put it in column A, or column B or maybe even row 3 - it depends!

The LLM does that part non-deterministically.