I just copy the google definition of PSA for you:

What PSA level indicates cancer?
In the past, PSA levels of 4.0 ng/mL and lower were considered normal. However, some individuals with PSA levels below 4.0 ng/mL have prostate cancer and many with higher PSA levels between 4 and 10 ng/mL do not have prostate cancer (1). In addition, various factors can cause someone's PSA level to fluctuate.

ExoDx is from urine test. Below is from their website:
What is the ExoDx Prostate Test?
The ExoDx Prostate Test is a non-invasive, non-DRE, urine test used as a risk assessment tool to provide risk probabilities for aggressive prostate cancer. It relies on cancer-specific genomic biomarkers found in the urine. Patients below the cut-point of 15.6 are considered at low risk of having high-grade prostate cancer. Patients above the cut-point of 15.6 are considered to have higher risk of high-grade prostate cancer. The doctor and the patient should discuss the patients’ ExoDx Prostate score in a shared decision-making process including all relevant factors and make a decision as to whether or not to proceed with a prostate biopsy.

Once he gets his MRI result, his doctor will look at all 3 tests and decide if he needs a biopsy. If he does, make sure he asks for a transperineal biopsy not transrectal biopsy.

Good luck to him.