MajorGeeks published a tutorial about how to change the minimum and maximum PIN length in Windows 10.
How to Change the Minimum and Maximum PIN Length in Windows 10
Windows 10 offers the option to use Hello PIN, a 4 digit number that you can use to log into your computer. By default, your PIN is 4 characters, but you can specify any number you like.
How to Change the Minimum and Maximum PIN Length in Windows 10 - MajorGeeks