Attached is a snapshot of the same security (ESH8) in three different charting programs (from left to right Ninja, QuoteTracker and AmiBroker) using the same datafeed (InteractiveBorkers).
In each chart I have indicated with a green arrow the volume for the current bar. Both QT and AmiBroker display a volume levels of 15K while Ninja is showing 11K. I have notice this discrepancy on every bar i.e Volume shown by Ninja charts is lower by 4-8K on average per bar.

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