Loan payments vs financial calculator

[Geert Janssens]

Hi,

I am trying to setup a scheduled transaction for a loan.

At this moment I didn't receive the full table of payments from my bank yet, 
but the first payment has been made.

Using the financial calculator in GnuCash, I find that the numbers fit:
I have 12 payments, for the amount that I loaned, with the interest we agreed, 
the monthly payment calculated very closely matches what the bank charged me.

However, if I try to set this up using the Mortgage and Loan druid, I end up 
with one payment less (11 instead of 12) and the amount per payment is too 
high.

Just for reference:
The loan is:
Amount: 4.000 €
Intrest: 6.6% (or near to it, I didn't get the final number yet)
To be paid in 12 monthly payments of 343,53 € each.

The financial calculator gets very close to this.

However the druid gives me 11 monthly payments of 345,37 € each.

Where's the difference ?

Thanks,

Geert