What is Trading Capital and what should I input in it?

In the DPR System there is a Trading Capital field.  This feature is intended to help calculate the number of shares a user should purchase of each ETF listed on the DPR page.

A user should input the amount in this field that represents the total available trading capital including margin.  For example, if a user has cash $1,000 available and wants to use x3 margin, then $3,000 should be inputted for Trading Capital.