Calculations not matching chart that comes up

Hi there,
A client whose site we have this plugin installed on brought this to my attention. He did some test calculations and says that the calculations with the calculator that he made do not match the chart that shows up. See screenshot: https://www.screencast.com/t/hE1jHlF82

Here is what he said: “By my calculation it should be $1,389.35 per month under this scenario. However, on the website it calculates the payment as $1,384.42 which does not match the chart the website brings up, which states the payment should be $1,393.98. I did a number of scenarios and all the calculations are off by a few dollars. I could live with the few dollars off however, the chart must match the calculator. We are in a business of numbers, so this matters greatly.”

Is there any way this can be fixed?