"Year to date" sales for 2018, 2019, 2020, and 2021 sales are shown in series at the top of the table and then just below a comparison of 2021 versus 2020 and 2021 versus 2019 is displayed.
Check out Xbox Nation's comparison of Guardians of the Galaxy on Xbox One S and Xbox Cloud Gaming. Both ran on the one console to make sure the test was done on the same hardware.