The space-before property specifies the value of the space-specifier for the space before the areas generated by this XSL-FO object.
The space-after property specifies the value of the space-specifier for the space after the areas generated by this XSL-FO object.
A space-specifier have the following components: minimum, optimum, maximum, conditionality, and precedence.
Minimum, optimum, and maximum are lengths that define a constraint on a distance, specifying that the distance should preferably be the optimum, in no case less than the minimum or more than the maximum.
The conditionality component specifies whether a space-specifier has effect at the beginning or end of an area. Possible values are retain and discard.
Precedence is either an integer or the special token force.
|space||Specifies the minimum, optimum, and maximum values for the
space before or after areas generated by this XSL-FO object and the
conditionality and precedence of this space.
Default value is: space.minimum=0pt, .optimum=0pt, .maximum=0pt, .conditionality=discard, .precedence=0