1. Click the No comparison button in the toolbar. It turns into vs <dates> and two extra date boxes appear, pre-filled with the previous calendar month.
2. Adjust the comparison Begin/End dates if you want a different baseline.

Every card then shows a coloured badge with the percentage change (green up, red down, grey flat) and a line such as "$1,250.00 previous period" under the value; the Gross Volume card shows the previous amount too. If the previous period was zero and the current one is not, the badge reads +100%; if both are zero it shows a dash.

Click the button again to switch the comparison off.