[otrs] Noob - customising Customer User fields

Hello Everyone, As I'm a noob to otrs, I hope you don't mind this very basic question. I'm wanting to add some phone fileds to the Customer User panel, as per the first steps documentation. I've added three fields to the database table for Cellphone, Direct, and switchboard, and am looking at the "CustomerUser stuff" section of Defauls.pm, which is quite long. I want to keep my Config.pm as simple and short as possible, so the question is: To make ANY changes in a given section, does the WHOLE section need to be present in Config.pm, or do ONLY the lines which differ from the default setup need to be there (for me just the Map array)? Thanks for your answer :-) Cheers! Marius