Can anyone help clarify these elements when adding a bar element to a rendered Table?

Specifically:
- Is there a way to rename the bar chart header? Currently, when you add a bar element, it creates a new field to the existing table. This field is blank. Is there a way to give this new field a name?
- What are the two values indicated in the header to begin with? My set min for the axis is 0, why does it start at 100. What does 100 indicate? Likewise, what does 414 indicate?
- What are the thing grey bars at the end of each bar chart? The max value?