In section Search related to channel are shown the trends of the Search associated with the Channel, in terms of number of tweets collected.
Interacting with the buttons on the top left of the graph or interacting with the curve below the graph you can restrict the period to display.
In section Daily mumber of tweets/retweets for channel you can view the progress of the selected channel in terms of number of tweets and retweets per day.
As for the chart of the previous section, using the buttons on the top left of the graph or interacting with the curve below the graph
(which represents a view of the entire data set), you can select a specific time period to display.