more doc

tabxlsx.md

@@ -34,7 +34,8 @@ The code itself mimics that of openpyxl.
 The `headers` arguments defines the default order and formatting of the provided
 input data, which is `List[Dict[str, CellValue]]`, so each row does not have an
 implicit order. Using `["b:.2f", "a"]` shows the `"b"` values first formatted with
-two digits after the decimal point. Then `"a"` and then the rest.
+two digits after the decimal point. Then `"a"` column follows and then the rest in
+alphabetic order.
 
 ### run tabxlsx.py