envelope value not displayed in specified units

I posted in the sonar forum a question that I should have put here instead, sorry. Here is it:
SONAR 8.3.1 displays the values of envelopes as 0...100%, although my plugins report parameter info as specified by DirectShow and the Cakewalk plugin SDK as far as I can see.
The plugins receive queries for paramter info through IMediaParams::GetParamInfo(ULONG dwParamIndex, MP_PARAMINFO* pInfo), and I verified my plugins write all the fields in the MP_PARAMINFO struct pointed to by pInfo correctly, yet SONAR still display the values as 0...100%.
An example of MP_PARAMINFO fields:
mpType = MPT_FLOAT; mopCaps = MP_QUADS; mpdMinValue = -20.0; mpdMaxValue = 20.0; mpdNeutralValue = 0.0; szUnitText = L"dB"; szLabel = L"Gain";
I'm only finding this problem with SONAR, other hosts are displaying the values correctly. I mean, for the former example, SONAR displays 0...100%, and not -20.0 to 20.0 dB as expected and as other hosts show.
I'm clueless, and I'd be grateful if someone at Cakewalk could point me to the right direction. What might be making SONAR not to use the info I put in MP_PARAMINFO when displaying the value?