How do i keep a numbered list in mail merge the same in each document?

I am doing a mail merge document which has a numbered list 1 – 8. When i merge the document the first time the list in each document is 1-8. However, if i go back into the document after i have saved it and closed it the numbers change in each document. The second document will be 9-16, the third document will be 17-24 and on and on and on. The IT trainer in our company has not been able to figure this out. Any assistance is greatly appreciated. I am using Word 2007.