pre-installed lease calculator not working

the lease calculator which comes with this plugin is not working, the results tab are showing grayed out, when i checked the formula with field tables, there is no fieldname6, but in the formula it is showing, i think may be i have messed up a little unknowingly, could you please write down the formula taking below values

fieldname2 as Loan Amount
3 as interest
4 as no. of months
5 i kept as page breaker
6 as Monthly Payment
7 as Total Payment
8 as interest amount
is there any way i can also add a down payment field