Usually at the Supreme Court, the only number that matters is five. Or so Justice Brennan (allegedly) said. But with respect to the leak investigation, the magic number is 97. According to the Marshal's report, "97 personnel" were interviewed for a total of "126 formal interviews." Apparently, "many" personnel–no more than 29–were "interviewed more than once." How do we count up to 97? We can speculate.
The report identifies two categories of personnel: "temporary (law clerks) and permanent employees." I do not think the nine Justices would be included in the category of "permanent employees." Indeed, it does not seem likely that the Justices were even interviewed. (See update below)
In OT 2021, there were a total of 37 law clerks. Each of the nine active Justices had four clerks, plus Justice Kennedy had one clerk who was likely (though not confirmed) detailed to one of the chambers. (In recent years, the Kennedy clerk spent time in the Gorsuch and Kavanaugh chambers). These numbers would suggest that there were 60 permanent employees who were interviewed.