If the amount has changed in real life, update the item in the scenario you use as your current picture.
Keep the old version when it still teaches you something
- Update the existing scenario when you are correcting an estimate or recording a lasting change.
- Duplicate the scenario first when you want to compare before and after.
- Create a separate Once item when the change is a one-off cost, not a new regular amount.
Check the frequency as well as the number. A weekly amount entered as monthly can make the result look surprisingly different.
Tip: Change one item, save it, then look at the monthly result before changing anything else.