How are Potential ongoing monthly repayments calculated on CCPC.ie for a mortgage?

[kirkwood]

I am currently making an excel for the mortgage rates listed on CCPC.ie

A
Product
BOI 4 Year Green HVM Fixed LTV >80%

B
Term
20

C
Initial
4

D
Follow On
16

E
Initial Interest
2.9

F
Follow On Interest
4.5

G
Mortgage
384300

I matched the initial interest monthly repayments ((2112.3) on the site using the PMT* formula, but my Potential ongoing monthly repayments show €2431.27 with same formula, whereas the site shows €2371.39.

Any idea where I might be going wrong?

PMT* = (Pv*R) / [1 - (1 + R)^(-n)]

where

Pv = Present Value (beginning value or amount of loan)

APR = Annual Percentage Rate (one year time period)

R = Periodic Interest Rate = APR/ # of interest periods per year

P = Monthly Payment

n = # of interest periods for overall time period (i.e., interest

periods per year * number of years)