Each of the enum members may be initialized with a value. If a value is not specified for a member, by default it's initialized to 0 (if it's the first member in the member list) or to a value greater by 1 than the value of the preceding member.
Module Module1
Enum Size
Small
Medium = 3
Large
End Enum
Sub Main()
Console.WriteLine(Size.Small) ' prints 0
Console.WriteLine(Size.Medium) ' prints 3
Console.WriteLine(Size.Large) ' prints 4
' Waits until user presses any key
Console.ReadKey()
End Sub
End Module