Laybye credit

Can you guys please explain to me what is laybe credit. After spending hours at THE FIX in Jabulani mall, along with my mother and sister first we struggled to register for a laybye card for my mum, as both me and my sister didn't have ours with, i then left the shop drove back home to get my laybye car. Coming back the male cashier with an awful attitude and no sense for customer service says my laybe car has R00 credit available. Kindly explain what credit should one have to make a laybye which require payment of 50% of the purchase price than the stated 10% of the foschini group laybye policy. To my understanding this is a laybye not a store credit/ account card so what credit should be floating and readily available on this laybye card! Please explain so i know the next time i come there! Very irritated as i have used this service before at festival mall in kempton park and never had a problem after fitting so many items and everything ending as an unfruitful exercise. Very ****es as some of the items were last either size or colour.