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Time & Sales Volume Question

I will like to know if any one knows what is the minus amount at the 19th hour if you look close is the first volume number after the close.

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Raw Data/Time & Sales
Data feeds often feed the cumulative volume to the application that is displaying the data to you. In order to show you what the volume on the last change or tick was the programmer will keep track of the previous cumulative volume in a variable (say v1) and subtract that from the current volume variable (say v0).

So each data point change will have its volume calculated by v0 - v1.

At some point, at the end of the trading day, the data feed zeros the volume and so the variable v0 becomes 0 and the variable v1 holds the cumulative volume at the end of the previous day. Implementing the formula v0-v1 causes the large negative value.

You will probably notice that if you took the absolute value of the large negative value (i.e. the positive value) then this will be the total volume for the day.

So in your example, ACPW probably had a total volume of 225,291 and MEH 790,200 etc.

It's basically a bug in the software which is fairly easy to fix if you send the programmer an email. Point the programmer to this explanation and he/she will probably be able to fix the bug in about 5 minutes.
Ah... very clever. I had to read through your explanation 3 times before I understood it though.