I've never heard of dB gain when talking about video recording, what does this mean exactly?
Decibel or also known as dB is an logarithmic unit. Look it up, if you need more info about it. As far as i am aware, 2 dB more would Double your exposure.
Since the Native (Base-) ISO äquivalent is ISO 500 on the Chronos 2.1, 24 dB Gain should be around 12000 ISO äquivalent, if i didnt get something wrong here.
Will have to do an Side-By side Comparison with an other Camera, to be able to say this for sure, but i think that should be about right.