You can add numbers to the past using the KPI module if you want a longer period visible. You can also edit these numbers if you notice a mistake. In this article, you can read how to do that.
Add numbers to the past:
Click the three dots on the KPI you wish to edit and choose "Edit KPI"
Scroll to the bottom of the pop-up window and click "show earlier months"
Add or edit your values for the desired months
If you need to go even further into the past, keep clicking "show earlier months"