Net change of futures uses yesterday's price at 16:15. Net change of VXX uses the 16:00 price ($18.31). 16:15 price was $17.90.
I was wondering the same trying to do a real time calculation of VXX using the future contracts on the CBOE but I assume this will be corrected by close...?
vix will go 15 eventuallyvxx will go 10