Actually, there is no mistake. The quote I gave you was on Friday April 17 at 12:30PM so it did not show the entire day session.Quote from local_crusher:
No! Your volume quotes are wrong. (seem not compounded over exchanges)
SPY VOL Thursday: 335M
SPY VOL Friday: 263M
Pls check Bloomberg
Below is the chart of SPY vs ES.D. The blue line on the very bottom is the 20 period moving average of the ratio of Price*Volume*Bigpointvalue of the 2 instruments. The data showed about a 3.75x higher total dollar amount traded in the S&P500 futures ES compared to the SPY etf. Not quite the value of 5x I quoted earlier, but 5x is pretty close to the 4.90 daily value (red line, bottom panel) reached on Friday.
I don't think that's important though. The best form of education is experience rather than a classroom setting.