The plugin uses EAPR by default. You have the option in the settings to change this to nominal APR when calculating repayments.
According to Wikipedia: The term annual percentage rate of charge (APR), corresponding sometimes to a nominal APR and sometimes to an effective APR (or EAPR), describes the interest rate for a whole year (annualized), rather than just a monthly fee/rate, as applied on a loan, mortgage loan, credit card, etc.
Calculating Effective APR
The formula is:
r = (1 + i)1/n – 1
r = rate per period
i = annual interest as a decimal (eg: 8% is 0.08)
n = number of payments in a year
Given 14.9% interest per year with monthly payments the sum is:
r = (1 + 0.149) 1/12 – 1
r = (1.149) 0.8333333 – 1
r = 1.01164 – 1
r = 0.01164
r = 1.164%
The nominal APR for monthly repayments would be:
r = 1.242%