We would like to informed you that in the Customer Group option(Management Console>>Operations>>Business Partner>>Customer Group) there is 1 customer group that is marked as Default, so while you will create new customer
then by default this customer group will assign to new customer. If you want then you can change to another customer group.
The default Walk-in customer(Cash customer) is for sale which is defined in the store definition in the Management Console(Administration>>Retail Configuration>>Store).