When selecting a project, the project dashboard is opened. The dashboard shows you the number of valid and spam submissions over time in a chart.
The gray line with the text Statistic only shows you to which date you can expect the submissions in the submission list. All submissions on the left side of this line have already been deleted.
Date range selector (Added in v1.1)
You can choose the visible date range with the date range selector in the top right corner. The dropdown shows only the possible values, according to the setting Statistic storage. If you choose 3 months in the setting, for example, only the options up to 3 months are visible in the dropdown in the dashboard.