Master Clock Setting - What does it do?

Within the Audio Hardware preferences page there's a 'Master Clock' setting available for MME devices (on Windows). Anyone know what this actually does and when one might need to change it?

I was under the impression that the audio clock was set within the soundcard, and would typically either be the soundcard's internal reference, or an external reference plugged into the card).

Anyone ever used this Master Clock setting in Audition to actually solve a problem?

Many thanks.