Fix copy-paste error: id xyz should default to 0

In order to produce the correct result from the linearization equation, id
components should default to 0 while range components should default to 1.

adoc/chapters/programming_interface.adoc

@@ -12360,15 +12360,15 @@ a@
 size_t y() const noexcept;
 ----
    a@ Return the value of dimension [code]#Dimensions - 2# of the [code]#id#
-      object, or 1 if [code]#Dimensions < 2#.
+      object, or 0 if [code]#Dimensions < 2#.
 
 a@
 [source]
 ----
 size_t z() const noexcept;
 ----
    a@ Return the value of dimension [code]#Dimensions - 3# of the [code]#id#
-      object, or 1 if [code]#Dimensions < 3#.
+      object, or 0 if [code]#Dimensions < 3#.
 
 a@
 [source]