Partitioning same drive for Windows (OpenCore)

iMac (Retina 4k, 21.5-inch, Late 2015) iMac 16,2

OpenCore Legacy Patcher 1.5.0

macOS Sonoma 14.5

I want to install Windows on the same drive I have Sonoma on (external SSD), but trying to understand the "Formatting the Target Drive" section on OpenCore's website https://dortania.github.io/OpenCore-Legacy-Patcher/WINDOWS.html#disk-partitioning-and-formatting is confusing for me especially Note 3. Can anyone make it easier to explain since there is no proper video on it?