RoleType Enum description

What type of issue is this?

Question

What SharePoint development model, framework, SDK or API is this about?

SharePoint CSOM

Target SharePoint environment

SharePoint Online

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

Microsoft.SharePoint.Client 16.1.0.0

Issue description

I want to have more clarity on the RoleType enum in CSOM SDK / REST API.

Most of the RoleType values have a clear description written here:
https://learn.microsoft.com/en-us/previous-versions/office/sharepoint-csom/ee536725(v=office.15)

But on this website there is no description at all:
https://learn.microsoft.com/en-us/dotnet/api/microsoft.sharepoint.client.roletype?view=sharepoint-csom

In my current Microsoft.SharePoint.Client 16.1.0.0 SDK there are the following roletypes available:

public enum RoleType
{
	None = 0,
	Guest = 1,
	Reader = 2,
	Contributor = 3,
	WebDesigner = 4,
	Administrator = 5,
	Editor = 6,
	Reviewer = 7,
	RestrictedReader = 8,
	RestrictedGuest = 9,
	System = 255
}

Thus the following values don't have a good description what they represent:
Reviewer = 7
RestrictedReader = 8
RestrictedGuest = 9
System = 255

Question 1: Can these be described as well?

In my current code where I set/delete role assignments, but I keep off the Guest and RestrictedGuest, because they cannot be added or deleted. The Guest role name is described as "Limited access".

Question 2: Should I also ignore the RestrictedReader and System because they are also readonly?