ASVAB is a test that is offered to 14,000 potential recruits each year. Given the abundance of education and training available, ASVAB is not designed to test you on an astronomical level like nuclear physics.
This is an exam designed to test you on the standards of high school reading, science, math, speaking, and more. Click here for more info to know the level of education varies depending on the high school in the country, this exam aims to test the average.
Potential recruits have many testing strategies and skills. The students get motivated and become hardworking by the recruiters. If you study and prepare properly, you will get quality results.
Remember to ensure an adequate and consistent exercise plan with sufficient exercise time. Break down the topics you want into subtopics and focus on one concept per day. As you study each topic, take notes, and practice the questions to ensure you have the resources to review them.
If you feel like self-study isn't enough, get a recruiter. Don't let a lack of knowledge hold you back. Find someone qualified to help you with each topic and let them provide you with information so that you are sure you are doing an individual exercise.
If you work very hard using the above methods, you will find that your training results improve. And remember, you don't have to score 100% to qualify. The AFQT 50 is sufficient for most branches of the US military.