Volume spike "removal" is not really possible - each quote is stored with its cumulative, not incremental volume. That is how they come across in the feeds, and that is how they are stored. Now, the display problem - here is how the "Scale by Max" checkbox works:
If it is checked, then the maximum visible value is calculated and the scale is set to 1.05 of the max.
If it is unchecked, then the average visible value is calculated and the scale is set to the lesser of 10 times the average or 1.05 times the max.
So if there is a BIG spike (more than 10 times the average volume) , and "Scale by Max" is unchecked, the scale will be set to a value that is less than the spike, and the spike bar will go out of bounds.