The Volume Distribution Chart is a statistical interpretation of the current sentiment on each stock in graphical format.
The Volume Distribution Chart goes through all the transactions, broken down by the volume done per trade and groups each trade into four different bars, differentiated by "Buying up" and "Selling down" activity. Simply speaking, for the 4 sets of bars, the highest set is likely to be traded by institution/super dealers, while lowest set usually represents retailers.
Each sets of two bars represents the lots being 'Buy Up' or 'Sell Down' at that volume quantity. When we say 'Buy Up' (the lower bar with the stronger colour) it refers to the more impatience buyers snatching up the lots queued at the selling price, and we use 'Sell Down' (the upper bar in the fainter colour) to mean the panicky seller selling their shares to the buying queue.
Each bar can have up to 4 different colored parts and it represents the period that the trade occured. Please refer to the legend for reference.