When speaking about a Bar Chart, there are no X and Y axes, only Category Axis and Value Axis.
The Category labels are simply whatever you have in the category column of your table's Chart Range. To change what is there, edit it.
It would be difficult to be more specific without knowing how you made that chart. There is no direct way to make a Chart like that in Numbers since Dates aren't allowed as Values. We would normally use week-number instead, where week-number is a numeric representation of the time elapsed since some base date.
Jerrold....thanks for the reply. While you didn't answer my question exactly (I know I was a bit vague), you did put me on the right path. I was trying to get the Category Axis values to change on the chart whenever I updated them in the table itself. I couldn't figure out why they weren't but I think I have now.
I noticed that in the Category Axis field (Inspector) it had the actual typed names of my tasks from the table instead of the cell locations. So...."Task 1" instead of "Table 1: C7". I cleared out all of the text in the Category Axis field, which removed it from the chart. then I just clicked on the fields in the table and it populated the Category Axis blank with the table/cell info instead of the text. So now when I update one of the fields, it updates the chart because it's pulling from the cell data every time.
I'm not really sure why Number, by default, enters the text into the Category Axis when making a chart instead of putting in the corresponding cell locations, but whatever. I got it working now and should be good to go going forward, thanks for your help.
Numbers Category Charts are happiest when the Category Axis data column is a Header Column or Row. It's difficult to coerce a Category chart to use the labels in a non-Header category field. Header Column/Rows are formatted as Text by default.
Conversely, it's difficult to get a Numbers Scatter Chart to take X-values from a Header column. You get the picture - plan ahead.