Also when I put in the slices, and It is 100% photography it comes up as 50% and 50%. Shouldn't it come up as 100%? Why would it create more than 1 slice?
Hard to say when you haven't described the charting options you selected for your chart (other than the style of the chart that is...)
What is your percentage field intended to represent? The percentage of the total records being charted that have a specific medium selected?
I may be guessing wrong as to what you want to do, but your slice data series can be set up to refer to a "count of" summary field that counts your records. Then you specify a data source option of "found set, summarized data", perform a find for the records you want to chart and then sort them by the medium field to group them by the value in this field.