I am sometimes asked what the LHF stands for. Well, it stands for Low Hanging Fruit, a phrase which refers to doing the easiest and fastest things first. Think about it. If you're picking apples and are in a hurry to fill up a basket, you are going to pick the apples hanging from the lowest branches first, because that's the fastest way to reach your goal. You are probably not going to haul out the tallest ladders and pick from the highest branches.
Similarly, if your goal is to pass the HiSET Math Test as fast as possible, it makes sense to focus on the easy and medium level skills across all math topic areas, and not get bogged down in advanced algebra and geometry skills.
There are plenty of comprehensive math curricula available for students who want a more comprehensive math experience. The LHF Series is designed for a specific student: one who is in a hurry to pass the HiSET Math Test.