Testosterone levels can vary considerably from individual to individual. It is somewhat common for a young person (21 years of age) to have a low level of total testosterone reported at 310 ng/dl. The reasons that individuals have low levels of testosterone are not clearly understood. Basically, it has to do with the production of the testes of subnormal amounts of testosterone. This can be a result of genetic factors, pituitary gland factors, medication interference and other interfering substances and factors. The levels of 364, 432 are in the low range of normal. It may not be a problem depending upon the degree of symptoms, fatigue, weakness, low libido, etc.
A trial dose of testosterone in a moderate amount may be beneficial to determine if this would be beneficial from a medical perspective. I feel that without a trial dose and follow up blood tests to determine increased levels one cannot know for sure.