That doesn’t mean what you think it means. You are not twice as likely to die form a stab wound, if you are treated quickly fort a stab wound you are much more likely to survive compared to a gunshot wound. You need to look at the incidence of death percentages:

“(Gunshot wound: early, 2.0% vs. late, 4.9%; Stab wound: early, 0.2% vs. late, 1.1%)”

So a stab wound if treated early has a 0.2% chance of death compared to a gunshot wound which has a 2% chance of death, meaning gunshots are 10 times as deadly. Under late treatment its 1% chance of death for stab wounds, and 4% for gunshots, so gunshots are 4 times as deadly.

Even late treated stab wounds are half as deadly as early treated gunshots. Gunshots are far more deadly than stabbings.