TradeStation Help
Volume bars plot bars based on a specified trade volume. For example, you can plot bars every time a certain number of shares are sold; for example when 100, 200, or 1,000 shares are sold. A new volume bar is built every x-number of shares sold (where x is the volume you specify).
Volume bars record the Open, High, Low, and Closing prices for a specified volume of shares traded. Volume-based bar charts are helpful for traders interested in analyzing trading volume.