It means it is the proper sectional density. I understand that fast monolithic do not require the SD of a lead projectile. But SD is a measurement that will predict how lead will penetrate. If one chooses to shoot let's say a 180 grain round ball at a mature elk, one will be best trying to avoid impact with bone. I try to stay above .25 for lead based bullets on elk. But like I say I have killed with arrows, and I am sure a 22 mag would also work. So basically a 385 grain or greater 50 caliber I would personally consider as adequate elk " medicine". But 2 each his own.
