Each System you work in is contained inside the Clients module. This is where you set your Pay Scales if you pay your techs a fixed Percentage of revenue. You may setup as many Pay Scales as you wish.
The illustration above is the anatomy of a Billing Code. Every Billing Code is a record onto itself with all of the details pertaining to that particular code. Override prices on codes where wish not to pay a straight percentage.
This is a Table View of Billing Codes. It's not unlike an Excel spreadsheet. The Table View gives you an array of viewing options.