Account Balance not showing correctly

Sir,

Suppose , i have posted an invoice of Rs.200 against a customer and after some times i recieved payment from this customer of Rs.200 So, accout balance of this customer should be zero.. But when i see the account balance from business partner master data , it should me Rs.-400 in accout balance field but when i navigate through orange arrow in to accoutn balance details , there i get zero in balance due field?? ie. it is showing coorectly in details of account ballance but in the business partner master data it is not showing correctly??