How is "vs. Prev Period" calculated?

The “vs. Prev Period” metric is relative to the period chosen. For example, if you select “Feb 2022”, that is a month period, so it will be relative to growth or decline from the previous month (Jan 2022). Same if you select “2022”, growth or decline will be compared to the previous year (2021).

In the situation of selecting two months, using Jan and Feb 2022 as an example,  "vs. Prev Period" is going to be relative to the two months closest to, but not including the latest month selected (February), so Jan 2022 and Dec 2021.