You can display charts with an Absolute Scale, Logarithmic Scale, or a Percentage Change Scale. The Lock Scale and Autoscale options determine whether the Price Scale will adjust based on changing chart data. This is done by a Right-Click to the Price Scale on the right side of the Chart and selecting the desired Scale.
Absolute Scale is the default scale and it will automatically select the appropriate scale based on the size of the chart window and the range of price data being displayed. To use Autoscale, all of the Scale options seen above must be unchecked.
Logarithmic Scale divides the chart logarithmic scale (ie 1, 10, 100, 1000) which can aid visualization when the chart covers a large range of values.
Percentage Scale divides the chart y-axis into 10% sections
Lock Scale will fix the y-axis so that it does not move even if the price should move out of the visible part of the chart. this is useful if there is some horizontal element such as a stop limit that the user wants to remain in a fixed position. Lock Scale is evident by the icon of a padlock at the top right of the vertical scale.
Autoscale is the opposite of Lock Scale. In the case of a live chart that is still updating or if the user is scrolling across time and the range changes Autoscale will attempt to keep the entire chosen time range of the chart visible.