Pivot Table not displaying percentage in correct format

[KJG03]

Hi. I'm finding that when I create a pivot table the column that I have formatted as a % that I have typed in comes through into the pivot table as a negative number. E.g. The numbers vary even though I have used the same % figure. 50% displays as -423355.90738. How do I get this to display in the % format as the 50% that I have typed in the spreadsheet. I have tried doing a cell format to percentage but it just puts a percentage symbol after the long negative number.