The "30" you see in the Micrometer dial is .030". You read the 2.1" from the base of the micrometer and add the dial reading so you end up with 2.130". In metric, the center to center measurement of the stock links is 54mm.
I checked my BMW 2" lowering links and they measured approx. 70mm center to center. I also chekced the Koubalinks 1" lowering links and those measured, not surprisingly, approx. 62mm.