What happens with --increment when using irregular mask?

[SopalajoArrierez]

Hello, folks.
I could not find the answer to my question in the Wiki, so I am going to pose it here:
If I make a mask like "?u?d?d?d", does --increment mode builds this automation?

Code:

?u
?u?d
?u?d?d
?u?d?d?d

or maybe this other one?

Code:

?d
?d?d
?d?d?d
?u?d?d?d

I think the description at "Mask Attak in the Wiki" is ambiguous about this.

Thanks in advance.