If you swap the lines, you'll get the same effect as in the other columns. The "KILLS" column will be the same as "DAMAGE," "KPH," and "DPH."
from this line:
add_grid_label(row_gui, tostring(row.kills), column_widths.kills)
to this line:
add_grid_label(row_gui, format_big(row.kills), column_widths.kills)