All this is really saying is, according to this particular study, we can come to no conclusion on whether masks increase or decrease the spread of coronavirus. Or in other words, masks probably don't influence it one way or the other at all. If we take this data and compare it with other data we can also say the masks most people wear are an at best 20% reduction in the spread of the virus. We can also say that at worst they help spread coronavirus by some small amount.

Even in the best case scenario, a 20% reduction is meaningless in all ways. It won't matter on a population level, it won't matter on an individual level. On the contrary, for any at risk population (elderly e.g.) it will give them a false sense of security, promoting otherwise bad behavior because they "have their mask on."

Much more concerning than studies on whether or not masks help with coronavirus spread are studies on bacterial infections that cause pneumonia because of the types of masks people wear and the way they use them. Pneumonia is the largest cause of death from coronavirus, and many studies (before 2020) suggest reused cloth masks are the largest contributor to getting infected with those bacteria.

Based on a fair bit of study on this topic, my advise is don't wear a mask for an extended period of time. If you can help it, don't wear a mask at all.