The volume you see is the OTC exchange volume. The total volume is what comes across the ticker, summed over the day. I don't know of any place you can access the total volume except for software that captures every trade off the ticker. The only help I have found is software that captures each trade, dumps it into a fixed price bucket and lists the volume at each price. It is not my computer doing the capture or filling the buckets. I have to add up the buckets to get total volume. This information is based upon what I was told by an account specialist at TDAmeritrade.
For those wanting to learn more Google "Dark Pools" or "Dark Pool Trading". There are many debates, explanations, political posturing, and an abundance of outright lies. This true swimming with the sharks.
News 
Market Data 
Discover 
