Note Naming allows to switch between the two most popular note naming conventions.
In classical music usually "si" is designated as H and "si-flat" as B.
In jazz and some other modern styles "si" is designated as B and "si-flat" as Bb.
Device Latency section controls the delay between something is played and it actually sounds. Audio delay is controlled with Wave Latency field, MIDI Latency controls the delay of MIDI signal. Calibrate... button invokes Calibrate Delay dialog that allows to measure latency on your system.
Note: Wave and MIDI Latency values control the prefetch of playback data for Audio and MIDI correspondingly. Latency (the delay between the playback command and the moment when sound appears) may significantly depend on your sound card and system speed. Cheap integrated sound cards can have MIDI delay about 100 ms or even higher. It is recommended to calibrate at least MIDI latency before using WIDI. Audio latency is usually negligibly small. Accurate latency values are extremely important for using Synchronous playback.