This graph shows Active Daily Installs for Firefox. ADI data is noisy. Work computers for example are off over weekends. The data is also highly seasonal. The peak
of the year is usually around Christmas. ADI may underrepresent active users (ADU) since a user might be active but Firefox misses to check in that day. ADUs are assumed to be about 10% higher than ADI (ballpark).
Smoothing compares a window of 7, 30 or 90 days to the same window of time exactly a year prior and plots the difference. -10M on the graph means that 10 million users were lost year over year.