# Marginal notes overrun the paper even if only papersize is specified

The following seemingly innocent MWE:

\documentclass{article}
\usepackage{geometry}
\geometry{%
papersize={170mm,240mm},%
verbose%
}
\begin{document}
Foo.
\end{document}


Package geometry Warning: The marginal notes overrun the paper. Add 3.44473pt and more to the right margin.

Note that, by contrast to the question Warning message: "The marginal notes overrun the paper", here margins are not specified.

How can that be?

If you don't specify the width for marginal notes, geometry uses the default 65pt with a default \marginparsep of 11pt.

Its heuristics lead to a text width of 338.5863pt, over a 483.69684pt page width, with equal margins at either side, so the margin width is 72.55527pt; since 65+11=76 is larger than the available margin, a warning is issued.

If you specify just the paper width, geometry sets the text width at 70% of the page width, see section 6.5 of the manual, bottom of page 13, case S(0,0). Indeed, 483.69684*0.7 = 338.587788, which agrees with the stated text width, up to the usual TeX rounding to scaled points.

If you specify includemp, you get

* \paperwidth=483.69684pt
* \paperheight=682.86613pt
* \textwidth=262.5863pt
* \textheight=478.0042pt
[...]
* \marginparwidth=65.0pt
* \marginparsep=11.0pt


and no warning. But you see that the default values for \marginparwidth and \marginparsep are still used.