Update cartan.xml

Reworded for clarity

Author: JosephDayngerRuiz

doc/cartan.xml

@@ -167,10 +167,10 @@ gap> RClassBicharacterOfGroupHClass(H);
     <Returns>A matrix.</Returns>
     <Description>
       <Ref Attr="BlockDiagonalMatrixOfCharacterTables" Label="for a semigroup"/> 
-      returns a block diagonal matrix whose
-      block matrices along the diagonal are character tables of some group &H;-classes 
-      in each regular &D;-class of <A>S</A>.
-      The character tables are determined by 
+      returns a block diagonal matrix which has a mmatrix block for each 
+      regular &D;-class of <A>S</A>. The block matrices along the diagonal are 
+      character tables of some group &H;-classes in each regular &D;-class of 
+      <A>S</A>. The character tables are determined by 
       <Ref Attr = "OrdinaryCharacterTable" BookName = "ref"/> of 
       <Ref Attr = "Range" BookName = "ref"/> of <Ref Attr="IsomorphismPermGroup"/>
       of <Ref Attr="GroupHClass"/> of <Ref Attr="RegularDClasses"/> of <A>S</A>.