How to realign my checing account ?

[Bob Alexander]

As some of you have noticed I started using GnuCash a few weeks ago and 
precisely June 16th.

I connected to my bank and jotted down my bank account balance on that 
day and entered it as an initial equity with a transfer to my bank 
account and from there onwards have entered all expenses.

For some days all was aok and the balance of my online bank account and 
my GnuCash was precise to the (euro)cent !!!

Problems started trickling in when I received evidence of OLDER 
transactions which I wanted to enter. For example I received my credit 
card account which was prior to June the 16th.

Probably because of this, even though I have registered all of my 
expenses, my bank account and my GnuCash account balance do not have the 
SAME value :(

What is the methodology to redress this ?

Sorry if the question is confused but it duly reflects my state of mind 
... confused.

TIA,
Bob