Filter cutoff frequency and calibration?

Received my Poly Cinematic and have been having a good play with it. Some really amazing sounds can be squeezed from this module!

I am having a bit of an issue with the filter though. The cutoff frequency doesn't seem to go below ~300Hz, with 12oclock sitting at about 3k - which is quite high for a filter in my experience. It means most of the knob past 12 oclock is rarely used with lowpass, and I'm not able to actually close the filter (300Hz is very much in the audible range).

Is there a way to calibrate the filter, or is there as issue with my module?

Edit: I should mention that this is with Key follow off and Env Depth at its lowest setting. Using key follow seems to bring the floor down a little for low notes (so it can definitely go lower), but I'm not always looking for this kind of modulation - I want it at 0 when the knob is at 0 with key follow off. Increasing environment depth increases the floor.