If your dataset has some missing data for some categories and you have created a visualization showing cumulative sums, then the cumulative sum will be in descending order. This may not be accurate as cumulative sum is adding up the current value to the previous running total.

To resolve this issue,  right click on the visualization, select "Properties >> Appearance" and under 'Time Series' section enable the "Compensate for missing values" option.



Selecting this check box will produce a bar or line value of the same size as the previous bar or line value instead of showing no value at all .Enabling this setting will temporarily add new rows with empty values for the missing periods so that they can be used in the calculation.
 

How to get the cumulative plot on Bar chart working when the dataset has missing values?