When defining the numbers in Subheader's settings, use the positions from the parent list of the constructed list, not the constructed list itself.
For example, if you have this predefined list:
and this constructed list:
Even though the constructed list is in the opposite order of the parent list, you still want to use the same Subheaders settings as if you were using the predefined list:
var subheaders = [
[1, 2, '<b>Alpha</b>'],
[3, 4, '<b>Bravo</b>']