order no repeate when i make invoice why

Hi guys i make report to sales invoices this report take data from sales invoice line table i see same order two time but with different quantity why how i solve this problem.our employee make sales order then ship then invoice it display in database as two lines but he make invoicing one time as following in sales invoice line table

document no sell to customer line no quantity order no

12 005 100 90 20

13 005 100 200 20

are this true

i think it must display as one order as following

12 005 100 290 20

what i want to display this line in database as

12 005 100 290 20

what i make to solve this problem

Possibilities may be

  1. More than one item in Sales Invoice line

  2. One order multiple Invoices

Check this things