<?Surf version="1.0" encoding="utf-8"?>
<fo:root Surfns:fo="http://www.w3.org/1999/XSL/Format">
   <fo:layout-master-set>
      <fo:simple-page-master master-name="test-page-master" page-width="8.5in" page-height="11in">
         <fo:region-body margin-top="0.4in"/>
         <fo:region-before extent="0.3in"/>
      </fo:simple-page-master>
   </fo:layout-master-set>
   <fo:page-sequence master-name="test-page-master">
      <fo:flow flow-name="xsl-region-body">
         <fo:block>
          This is a reference line for property set below.
    </fo:block>
         <fo:block space-before.optimum="50mm" space-before.minimum="49mm" space-before.maximum="51mm" space-before.precedence="force" space-before.conditionality="retain" background-color="silver">This element should have a space-before of 50mm.</fo:block>
      </fo:flow>
   </fo:page-sequence>
</fo:root>