Check this option to show cumulative data values in the time series plots that appear in the pop-up window at each site. This has the effect of showing how much a given measurement has grown over the time span shown in the plot. For instance, showing how much it has rained over the past 24 hours. Turn this feature off when you prefer to see the instantaneous values instead, such as how much it rained at each distinct sample period.
without cumulative plotting:
with cumulative plotting: