It prefers your own data and only goes outside when it has to. In Excel, for example, if it can work out a figure from your columns, it builds a formula. If the ingredients are missing, it searches for them. You can override this either way, for example by telling it to take the figure from the World Bank.
More in Accuracy and Checking
Why does my Copilot notebook show fewer references than I uploaded?
Because it is still loading. The notebook only counts the references it has finished indexing, so wait until everything has loaded and the count catches up. Separately, there is a limit to how much it searches in one go, so ask targeted questions and ask it to quote the sections it used.
How do I check AI output quickly?
Ask the AI to quote the exact source text under every statement, then use Ctrl+F to find each quote in the original. That turns a full re-read into a quick spot check. You still read everything, because AI removes the drafting work, not the responsibility for checking it.
Does AI always give its Sources?
No. You get clickable sources when the AI searches the web, but when it answers from your document or from what it learned in training, it shows no source unless you ask. Ask for the exact snippet, word for word, then Ctrl+F it in the document to confirm it is really there.