-Total amount to be billed, excluding taxes if they are to be added separately.
-This field is required if B<description> is a string, and should be left
-undefined if B<description> contains a list of products, as outlined in
-L<"Products list syntax">.
+This field is required if B<description> is a string, but should be left
+undefined if B<description> contains a list of products instead, as outlined
+in L<"Products list syntax">.