|As Robert Holdstock was left to his own devices (mostly) for the Trader's Manual for Elite, he coined the phrase LM to mean Light Mach, but it's long since been agreed that since injectors and the Torus drive allow you to go silly speeds, LM cannot be the equivalent of Mach since most ships on injectors would be going FTL. Therefore, it is assumed that LM is some kind of normalised, sales pitch kind of figure that doesn't actually represent a fractional part of the speed of light.
Note, that even if injectors and the Torus drive were FtL, it would still take years to jump from one system to another (with a handful of exceptions such as Laeden & Legees in Galaxy 1 - and that travel too would take much longer than a jump).
There is an insightful 2010 discussion of how fast one should choose to travel here on the BB. The Stranger's World suite of OXPs incorporates some of this thinking in terms of using rather more fuel when the speed is in the "red zone".