% row 1
> \cals@spanq@heights=macro:
->{0.0pt}.
% row 2
> \cals@spanq@heights=macro:
->{0.0pt}{0.0pt}.
> \cals@spanq@heights=macro:
->{0.0pt}{50.0pt}.
% row 3
> \cals@spanq@heights=macro:
->{50.0pt}{50.0pt}.
> \cals@spanq@heights=macro:
->{50.0pt}.
% row 4
> \cals@spanq@heights=macro:
->.