Cedric Charlier shows how to turn a running total into a periodic series of events with M:
When dealing with time series, you should always check if your time series are event-based or cumulative. For a time series with a step of one day, an event-based time series will contain the count of events for a given day. A cumulative time series will contain the sum of the event of that day and of all the previous days! In this blog post I’ll explain how to transform a cumulative time series into an event-based.
Click through for the code. You can do this in T-SQL as well by subtracting the value from its LAG()-ged value.