What this tool measures on one page
It counts the words and the sentences, the average sentence length and how much the lengths vary, the longest sentence, the share of the page that sits inside quotation marks, the filler words such as very, really and just, and any run of three or more sentences that begin with the same word. It also looks for raw formatting characters showing as text, for two different numbers given for the same thing, and for one name written more than one way. Every one of those is arithmetic. You can check any of it by reading the page you just pasted, which is the whole point: a report you cannot verify is a report you have to take on faith.