The 'format' property is only partially supported, where it is limited to the following values:
format : 0*1|a|A|i|I Perhaps someone could update http://xmlgraphics.apache.org/fop/compliance.html#fo-property-numberstring-sectionto change from yes to partial, with the following comment: Only '0*1', 'a', 'A', 'i', 'I' values supported.
