This is a terrible article. In this case, "lifeguard" is anyone in the 1000 employee lifeguard unit. The $392k is attributed to Fernando Boiteux who is an Assistant Chief in the LA Fire Department. Do you know a lot of people with 1000 people reporting to them who make less than 400k?
I wasted some of my time and tracked down the "Open the Books" org. It's a disingenuous non-profit that is part of the right wing bullshit industry. Think James O'Keefe, Newsmax, Heartland Institute, Sinclair, etc.