Standard of reference used when expressing levels.
"I just received my CD's and I have to tell you the transfer of lp's to CD's your company has done for me has exceeded all of my expectations. I'll admit when I sent my vintage lp's off to you I had some concerns, since they were irreplaceable, but you notified me, via email, the minute my lp's arrived and in less than a week, you notified me ..."
