[Groff] Possible bug in -doc

[Carsten Kunze]

Hello,

for generating

[n]"dd"

which means "an optional number followed by string dd" in a list I use

.Bl -tag
.It ...
<prev text>
.It Oo Ar n Oc Ns Dq Li dd
<text>
.It ...
<next text>

This is formated as expected by mandoc(1) and Heirloom nroff.
groff (current git) does indent <text> two characters less than
<prev text> and <next text>.

Is this a bug or invalid -doc input?

--Carsten