I downloaded the program to find antenna length, I got that much from looking at the drawing. The over all length I understand. But the length of the ends where the shielding is cut I don't see the length and the length of exposed of the exposed center wire. Like I said I can see what the over all length should be but that's all.
See this guys design for a worked example https://www.merseyradar.co.uk/airband-radio/home-made-coaxial-dipole-antenna-for-civil-airband then go back to your calculator program and enter in 128MHz and RG-213 and you should see the dimensions are the same. This should help you in your own construction. 73