Why is the sum of the total frequencies of phrases in the left column of the wordstat not equal to the total frequency of the original query?

Question

Search Engine Optimization

I always thought that when entering the original query into the wordstat, in addition to its total frequency in the left column, I get a list of phrases that include the original query, which means that the sum of the total frequencies of the phrases from the left column should be equal to the total frequency of the original query. When I checked this earlier, it would seem that everything converged. Now, a few months later, I entered the query "maintenance of fire fighting" and received a frequency of 538, while the sum of the frequencies of queries in the left column is 1893.
Question: did the algorithms change in the Wordstat, and if not, where did I make a mistake in my reasoning? If the sum of the query frequencies in the left column is not the total query frequency of the original query, then what does the frequency of this query add up to?

Answer 1

well, you add it up incorrectly,
for example, in the left column there is
maintenance of fire extinguishing equipment
and there is
maintenance of fire extinguishing equipment + in operation,
which is included in the request above, you need to delete subqueries if you consider mathematics