-(grob-property-description 'extra-extent-X number-pair? "enlarge in X dimension by this much, measured in staff space.")
-(grob-property-description 'extra-extent-Y number-pair? "see @code{extra-extent-Y}.")
-(grob-property-description 'extent-X number-pair? "Store extent. internal use only. ")
-(grob-property-description 'extent-Y number-pair? "Store extent. internal use only. ")
+(grob-property-description 'extra-X-extent number-pair? "enlarge in X dimension by this much, measured in staff space.")
+(grob-property-description 'extra-Y-extent number-pair? "see @code{extra-extent-Y}.")
+(grob-property-description 'X-extent number-pair? "Store extent. internal use only. ")
+(grob-property-description 'Y-extent number-pair? "Store extent. internal use only. ")