The stock was down 19.55 percent in NY, only 8.52 in Toronto.  The stocks should mirror each other percentage wise (within reason) as they do with other holdings that trade on multiple exchanges. This is just making up the difference, I'm glad it isn't the other way around tomorrow.  They will start the computer trades to keep the two markers moving in tandem, suspect today it isn't quite in synch, hence the odd discrepancy today. AH fixing it.