Issue in footerCallback

Link to test case: https://jsfiddle.net/BeerusDev/gbyks9r1/8/
I am trying to find an easier way to loop through all the days to get a count of all status so I can then create a simple switch statement to apply the count below my table instead of taking up like 160 lines in my other example. I call var data = this.data(), but it tells me in the next line data.flatMap is not a function? I am confused