Um, basically you have a branch that has leaves coming out of it. The oldest leaves are at the base, and the newest are at the tip. The very oldest leaves at the base are considered the leaf-line. Cut beneath them, and with Eremophilas no new growth will happen and the branch will likely die off (unlike with say a rose, where it's usually fine). Cut above, and you're more likely to create new growth.

Does that help? :)