FabFilter

I'm seeing some behavior I can't quite wrap my head around wrt to the way ratio behaves in an upward compression configuration. Downward compression is behaving as I would expect. For example:
A 1 kHz -6 dB sine tone sent into Pro MB with a single band that spans the entire spectrum.
Threshold: -12 dB
Range: -30 dB
Attack/Release: 0%
Ratio: 2:1
Knee: 0 dB (hard)
Lookahead: 0 ms

As expected, the above configuration produces a -3 dB tone. However, the following example confuses me:
A 1 kHz -6 dB sine tone sent into Pro MB with a single band that spans the entire spectrum.
Threshold: 0 dB
Range: 30 dB
Attack/Release: 0%
Ratio: 2:1
Knee: 0 dB (hard)
Lookahead: 0 ms

In this case, I would expect something like a -3 dB tone (6 dB below the threshold resulting in +3 dB amplification) or a +12 dB tone (6 dB below so +12 dB amplification) depending on how upward compression ratios work. However, what I see is a -1 dB tone. In no way can I deduce how a 2:1 ratio and a signal -6 dB below the threshold would result in +5 dB of amplification. I am pretty new to all this, but it would seem like I should get the exact inverse of the downward example. What am I missing? Thanks!

I've made some progress. Mainly, the realization that the range knob applies scaling when it is in upward compression mode helps explain when the actual amount of amplification varies. I hadn't noticed this because it says, quite distinctly, in the help text for Ratio: "In comparison, the Range knob limits the amount of compression or expansion, rather than scaling it." It's clearly scaling...setting a static ratio and increasing/decreasing the range also causes the amplification to scale. Kind of hard to determine how they interact, but in practice, it probably works intuitively?

You're correct: in normal expansion or upward compression modes, the range not only limits the amount of expansion, but also scales the amplification. We found that this gives a more natural / intuitive behavior that's comparable to how the range parameter works with regular compression.

Cheers,