The weekly audience does not match the sum of users for each day of the week
In most cases, the same user launches the app on different days during the week. The result is that this user is counted several times in the daily audience, but only once in the weekly audience.
For example, an app's weekly audience is 100 users. And if you sum up the number of users for each day, you get 110 users. This means that some users have run the app several times over the past week.