What does are you using a slotted port mean?

What is the best Port size? slot port length calculator I use to use this website for enclosure calculations, and just wondering if can get something similar but for L slot ports I actually found slot indonesia Calculation of cabinets and ports Copyright © Troels Gravesen The files The port length is not corrected to fit reality and if you use this file

slot center The box port can be calculated with a simple formula Box volume in cubic feet X 16 For