This study was simply a self-reported survey attempting to correlate past marijuana abuse with sperm counts, making it hard to control a number of factors such as honesty of self-reporting, exact historical use patterns, and representativity (the fact that 55% of respondents used an illegal drug when no attempt was made to generate such a high figure, when only 9.4% of the >12yo American population uses any illegal drugs, should be a warning that there may be external correlating factors not controlled for) of the general population. Most importantly, though, the study didn't actually measure the marijuana used, because it's an observational study and it's just measuring past use. You'd need to get the UMiss official research marijuana, and use a fixed dosing protocol over the interventional group, to make a claim about how much sperm counts increased as a result of marijuana use.
As the study notes, it's equally possible that high testosterone levels may predispose one to marijuana abuse, or that there is no causal link at all. Interesting and valid paper, but it does not justify any claims of A increasing B.