Rendering bit-depth, how is this determined?

I have a Focusrite interface with 24-bit recording/playback settings, and on Windows the recorded sample waveform reports 32-bit, which I assume is Renoise’s internal conversion. However, on my Mac I’m running it again at 24-bit recording/playback, but the sample waveform reports 24-bit.

Why does the reported bit-rate differ between platforms in this case? And on the subject of dithering, if I render to 24-bit, will Renoise automatically dither (since it’s from 32->24)?