Why does my carry forward bank balance show a negative balance from invoices?

I am new to FA and I was just about to start uploading bank statements when I noticed the starting or carry forward bank balance was negative (altho it shows as zero on summary). The negative balance seems to have been caused by created invoices? I know invoices affect the accounts but should they affect the bank accounts in this way too? It causing confusion in reconciling bank statements. P.S. my uploaded bank statements do not go back far enough so I intend to add manual transactions to get a complete record. The company incorporated in 03/10/07 & started trading 08/10/07.