see question above
Those new playback options were introduced in a recent release. They are for the use of audiophiles who may have hi-def (i.e., better-than-CD-quality) audio tracks in their library, but who wish to downsample them for use in computer playback.
For the rest of us, just leave them at the default settings of 44.1 kHz and 16 bits per sample, as shown below. This is consistent with CD-quality playback, and there is nothing to be gained by changing them.