The above graph visualizes the processing times of the NEW queue by upload month. It answers the question: how long did it take for a package which was uploaded in a particular month to be processed by the FTP team? This is subtly different from Federico's visualization of how much time a new package spends in the NEW queue: Federico's graph shows the age distribution of the packages while they are still waiting in NEW. This graph shows the age of the packages when they are leaving NEW.
The graph has different percentiles for the processing time. The k-percentile is the time that was beaten by k% of the packages which were uploaded to NEW in that month. The 50-percentile is better known as median; half of the packages where processed by that time and half took longer. The red-shaded intervals show the freezes for Debian releases.
If less than k% of the uploads in a month have been processed yet, the k-percentile remains undefined and is not plotted; this is why the graph lines may end a few months early.