Pivot table Custom Calculations

[theflash07]

I have a very large data set that I am using a pivot table to complete analysis on. The issue I am having is creating a custom calculation using the resulting pivot table data. Let me run you through a basic example. The lead and app numbers below are the result of a count function in a pivot table. I want to do the calculation (App/Lead) as percentage but when I use the custom calculation function I am getting the wrong result as it seems like the calculation is using something other than the "count" version of the field... help please?

Lead App
18827 6,083
5164 1,588