KOMA-Script and subcaption: wrong counting

Question

I'm getting a to-me strange behavior when using scrartcl and subcaption. In particular, numbering is doubled for each table with the default option captions=tableheading. Here's an image (code at the end) with captions=tablesignature, notice how the counter only increase by one if the caption is below the table (I'm not suggesting any causality here):

Here's the output when I switch to captions=tableheading:

I looked through the manuals of KOMA-Script, caption and subcaption but I didn't find anything that would suggest this behavior. Is it a feature? It's appreciate any hint on why this occur.

Here's the source

% bug(?), default setting for captions
\documentclass[captions=tablesignature]{scrartcl} %% same with scrreprt
% \documentclass[captions=tableheading]{scrartcl} % no bug
\usepackage{subcaption}
\setkomafont{caption}{\LARGE}
\begin{document}
\begin{table}
\caption{table one\label{tab:ind}}
\begin{subtable}[t]{.45\linewidth}
\caption{expenses}
\centering
\begin{tabular}{llr}
\hline
& Konto & \textsc{dkk}\\
\hline
& gnus & 3000\\
\hline
\textsc{(i)} & gnash & 146000\\
\hline
\end{tabular}
\end{subtable}
\qquad
\begin{subtable}[t]{.45\linewidth}
\caption{income}
\centering
\begin{tabular}{llr}
\hline
& Konto & \textsc{dkk}\\
\hline
& gnog & 100000\\
\hline
\textsc{(ii)} & gnus & 100000\\
\hline
\end{tabular}
\end{subtable}
\end{table}

\begin{table}
%% \caption{table two\label{tab:ind2}}
\begin{subtable}[t]{.45\linewidth}
\caption{expenses}
\centering
\begin{tabular}{llr}
\hline
& Konto & \textsc{dkk}\\
\hline
& gnus & 3000\\
\hline
\textsc{(i)} & gnash & 146000\\
\hline
\end{tabular}
\end{subtable}
\qquad
\begin{subtable}[t]{.45\linewidth}
\caption{income}
\centering
\begin{tabular}{llr}
\hline
& Konto & \textsc{dkk}\\
\hline
& gnog & 100000\\
\hline
\textsc{(ii)} & gnus & 100000\\
\hline
\end{tabular}
\end{subtable}
%% could also use \captionbelow
\caption{table two\label{tab:ind2}}
\end{table}

\begin{table}
\caption{table three}
\begin{subtable}[t]{.45\linewidth}
\caption{expenses}
\centering
\begin{tabular}{llr}
\hline
& Konto & \textsc{dkk}\\
\hline
& gnog & 370000\\
\hline
\textsc{(iii)} & gug & 552000\\
\hline
\end{tabular}
\end{subtable}
\qquad
\begin{subtable}[t]{.45\linewidth}
\caption{income\label{tab:ind3}}
\begin{tabular}{llr}
\hline
& Konto & \textsc{dkk}\\
\hline
& gmag & 100000\\
& glog & 218000\\
\hline
\textsc{(iv)} & gnus & 318000\\
\hline
\end{tabular}
\end{subtable}
\end{table}
\end{document}

Answer 1

It's not a bug, the behavior is IMHO correct. Since a table can contain more than one \caption, the caption package uses hints like captions=tablesignature to determine where it has to increase the table counter.

So when you use code like

\documentclass[captions=tablesignature]{scrartcl}
...
\begin{table}
% Table 1:
\caption{table one\label{tab:ind}}
% Table 2:
\begin{subtable}[t]{.45\linewidth}
\caption{expenses}
...
\end{subtable}
\qquad
\begin{subtable}[t]{.45\linewidth}
\caption{income}
...
\end{subtable}
\end{table}

the caption package sees two tables here: The one titled "table one" which ends directly after the \caption (and has no content, but the caption package does not know this!), since captions=tablesignature is specified. Afterwards a second table (without caption) is following. The table counter will be incremented for the second table because of the sub-tables. (A \ref to the first sub-table will therefore lead to "2a".)

If you really want to have a top caption even if captions=tablesignature is set, you have to give the caption package a hint about that, for example by using \captionabove instead of \caption:

\documentclass[captions=tablesignature]{scrartcl}
...
\begin{table}
% Table 1:
\captionabove{table one\label{tab:ind}}
\begin{subtable}[t]{.45\linewidth}
\caption{expenses}
...
\end{subtable}
\qquad
\begin{subtable}[t]{.45\linewidth}
\caption{income}
...
\end{subtable}
\end{table}

(A \ref to the first sub-table will lead to "1a" here, since the caption package knows that the content follows the \caption since \captionabove is used.)

But why the output is as intended when using the article class instead? This is not really true, if you use the article class and load the caption package with option tableposition=b, you will get the same behavior. My fault, I will add a section about the relationship of the position option with the figure and table counter in the next version of the documentation.

And why is there "no bug" if captions=tableheading is used instead? Well, this seems to be a real bug to me since "Table 2: table two" should be "Table 3: table two" here, I need to examine this...