Technically a cumulative frequency distribution is the sum of the class and all classes below it in a frequency distribution. Less than cumulative frequency distribution. To calculate the cumulative frequencies add the frequencies together.
The total frequency of all classes less than the upper class boundary of a given class is called the cumulative frequency of that class.
For example in Stem 0 we have only one observation and no predecessors. It can be computed by adding all of the numbers in the Frequency column above and including the current row. To calculate the cumulative frequencies add the frequencies together. The cumulative frequency in each row is found by adding all the entries in the Frequency column from the top row to that row.