Begin by telling the interviewer what your latest budget preparation was for. Was it for a large project? Or, was it a year-end budget? Share how large of a budget you were working with. In many cases, you will not be able to disclose exact amounts for confidentiality reasons, and that is okay! Instead, ballpark the number using phrases like 'tens of thousands' or 'hundreds of millions' to define your budget framework for the interviewer. Share how you determined where the money will be spent, who approved the budget, and how the budget is tracked against actual spending.