From this website
Integrated reduction gearbox, ratio of 2.43:1
This would mean that 5800rpm at the engine equates to 2387rpm at the prop (which, when rounded, is your redline of 2400), and 5500rpm at the engine equates to 2263rpm at the prop (once again, this matches your yellow arc when it's rounded).
So it seems the markings on your rpm guage are correct for the engine limits.
This is with no first-hand knowledge (I operated a Rotax 914 for a while, but never a 912, and I never really thought about the gearbox ratio that much!) - it's just based on what I've found with some help from Google.