The order of the substances can be switched. To do this, highlight the substance to be moved to a higher priority, click the number box to the left of the substance field and change the number of substance to a number smaller than that substance’s current number. Hit the Save icon, and the substances will be re-ordered.
Note: It is only possible to change a substance from a higher number to a lower number. Example: Change substance #3 to Substance #1.