Customer Credit Limit

I have an issue to resolve.The issue is that the credit limit for the

customer is 500,000.But when a sales order is created , it creates the

sales order upto 600,000 and gives error if amount exceeds 600,000 , I

have checked the customer credit management record in fd33 , also

checked fbl5n but no clue.I could not figure out that from where the

system gets 100,000 extra for credit limit.

Any ideas? I have just started looking SD module so dont know much

stuff.Any help would be appreciated.

Regards,

Aisha Ishrat.