Nope, it's around 10%. I'll try and dig up some stats.
Added by Edit:
Median price for SFH peaked in June 2007 at $439,900. January stats had them at $390,000; so we're down about 11%
http://www.findcalgary.ca/page_content-19.html#average
Your Realtor seems to be wrong in both amount and when the peak was.