This graph is fully interactive. You can simply move graph in time, by moving it with your finger.
The color dots shows the blood pressure category color of a measurement.
There is no need to select specific range of time like in other applications. With a help of scale on the bottom of a screen you can dynamically adjust a time range for which you would like to preview your measurements.
On the right corner of a screen in actionbar you can see a settings icon. Click it in order to pop up a settings menu. There you can mark which values you wish to be present on a graph.
A little bit more complicated is trend setting. Trend uses mean square error method to check whether e.g. your systolic values are growing in time or dropping.
If you select Trends, then they will be shown for each Systolic/Diastolic/Pulse/Weight depending on which is selected, but if none of mentioned is selected, then you will see trends for all your measurements.