Yesterday I noticed that the starting loan is always wrong calculated.
In the first try I started with a loan of 84000000$ in 1970 and payed ~900000$ per month over 60 month and the loan was repayed.
To test it I started a fresh save in 1900 on nightmare with 700000$ loan, a monthly payrate of 7400$ over 60 month.

All other loans that you take are calculatet right, but the starting loan isnt.