It is not clear from the context whether you are referring to taking multiple ASVAB prep tests in order to get a higher score or to somehow manipulating the number of ASVAB prep tests you have taken. If you are referring to taking multiple ASVAB prep tests, then it is generally recommended as a way to improve your score. The more familiar you become with the material and the format of the test, the better you will be able to perform on the actual ASVAB. However, it is important to keep in mind that taking too many prep tests can lead to burnout and decreased performance. It is also important to make sure that you are using a variety of prep materials and strategies in order to get a well-rounded preparation for the ASVAB.
If you are referring to somehow manipulating the number of ASVAB prep tests you have taken, then it is not allowed and could have serious consequences. The ASVAB is a standardized test that is used for military recruitment and placement, and any attempt to cheat or manipulate your score could result in your disqualification from the military.