He was writing a small page the involved doing a bunch of calculations based on some options. Various numeric values to be used in those calculations were stored in a set of arrays, sort of like this:
bar kept showing up like this:
See that last one? Our code for bar up above doesn't realize we want to put the value 5921 into element 0 of the array. It thinks we wanted to create an empty array with 5921 elements!
Changing the code to this fixed the problem: