Strangeness in Mortgage/Loan Repayment Druid

[Daniel Hannum]

I have a number of questions about the mortgage/loan repayment druid. 
BTW, I'm on 1.8.1 (redhat 9). So I this has been fixed, please let me 
know. I'm not prepared to grapple with upgrading (yet)... it was easier 
under Debian......

I have a car loan that, if you put the principal, rate, and term into 
any online calculator, you get $374.13. However, for whatever reason, my 
car payment is $374.09.

Now, when I put the principal, rate and term into Gnucash's druid, it 
comes up with 374.13, but that's not good, because that's not what I'm 
actually going to pay.

1. How do I force a particular loan payment? On the page of the Druid 
where you specify the 'Amount' and the accounts where the principal and 
interest will be, I tried replacing the "pmt()" expression with $374.09, 
but it seemed to ignore me; the next page still had 60 payments of $374.13

2. What does "pmt( 0.07900 / 12 : 60 : 18495.00 : 0 : 0 )" mean? 
Obviously, it's rate, term, principal, but what are the last 2 zeroes? 
Perhaps I shouldn't care. Or perhaps it could help to know.

3. If I were to start paying the loan off faster, with irregular 
amounts, I would have to put these transactions in by hand. Does it seem 
correct to take the balance after the previous payment, multiply it by 
7.9%/12 and use that as the interest portion? I would think that would 
be right, but when I try that with the current balance, it doesn't come 
up the same as what the scheduled transaction generator is producing... 
so you guys must have a different algorithm.

Any help would be appreciated.

dan