'Dynamics' not doing as I expected

Hi,

I'm new to Pianoteq (and creating music in general), so please forgive me if I'm asking a silly question.

I'm trying to adjust the levels of a piece of piano music that I'm mastering in Reaper with Pianoteq as the VST for the midi track. There's no other audio other than the piano. I'm trying to get to a target of -1dB max true peak and -14dB LUFS-I, but i'm struggling to understand how to use the Dynamics slider in PT Stage. According to the documentation I thought that the 'volume' slider effectively adjusts the loudness of fff, and the dynamics slider adjusts how much quieter ppp is than this fff, so I expected the difference between my true peak and LUFS-I to get smaller for the track as I reduce the dynamics slider. However when I render my track with 45dB dynamics, or 1db dynamics, the difference between true peak and LUFS-I stays broadly the same 16.1 vs 15.3. Both the true peak and LUFS-I go up as I reduce the dynamics, but I would expect this as my piece doesn't go harder than mf, so even the highest velocity notes will get louder as the dynamics is reduced, but I'm surprised that the LUFS-I doesn't go up even more than the true peak. I have turned the limiter off btw.

Thanks in advance for any help,