while doing f-32 error item 1000 should be created,a max 999 items allowed

Dear All

While clearing the customer line item by using f-32, we are getting error item 1000 should be created a maximum 999 items are allowed

& You are entering line item 998, a maxi of 999line items are defined

pl guide me how to clear line item, earlier 1600 line items are cleared

Vishvas