These controls are relatively self-explanatory and affect both the Synth and Strings sections.
Transpose
Octave- Shifts the overall tuning for the entire instrument up or down by an octave. Useful if you're using one of those fabulous 25-key MIDI controllers.
Split/Layer
In the case the name didn't give it away, Split/Layer enables easy independent assignment of the Synth and Strings sections to any continuous region of the keyboard.
To set the range for either the Synth or Strings, click the corresponding button between the LED displays; the left display flashes. Hit the lowest key desired for the range. The right side display will flash; hit the highest key desired for the range. The right display stops flashing and assignment is done. The top and bottom notes can be "manually" set by clicking on the LED displays and selected a MIDI note number from the popup menu.