First orientate the ECTM graphs such that the Mach line is vertical
(this is the constant parameter). Secondly, as it is CAS that you are
interested in, place your pencil point at the top of the CAS line and move the
pencil down the line (i.e. descending) - as you bring your pencil down the line
it will also be gradually moving to the right). Any movement to the right is an
increase in value!