Oh it's the size of the code in thousands of kilobytes?
It's comparing the size of the code.
Weird though, no? Am I wrong to expect a pie chart to represent the "total" or "100%" and the slices a portion of the whole? I could be wrong, but this seems like the wrong usage of the pie chart.
On those pies, the example SAAS product is the whole 100% and the tiny white slice is the custom alternative.