Each 1" change in scale equates to about half a tension set on average. For example, a 26.5" scale length on the Amethyst set would yield something in between SLT (Super Light Tension) and LT (Light Tension) in comparison to a 25.5" scale. 

The longer the scale, the higher the tension. A short scale has less tension than a long scale so you compensate by increasing the gauge of the strings.