What do these numbers on a package drawing mean?
It is the drawing issue date in ISO order (YY-MM-DD). It's paired with the symbol for first angle orthographic projection, so obviously belongs in a title block of a full drawing. Below is part of a title block of a more complete NXP drawing.



Edit: as confirmation see the NXP package drawing, which bears the same April 3, 2003 date. 

Edit2: The date format is specified to follow ISO order even in the ASME (U.S.) version of the GD&amp;T standard as follows:


  ASME Y14.100, 4.28:
  The method of specifying dates on drawings shall be
  numerical by year-month-day for entry in the “DATE”
  block. For example, June 10, 1989 would be indicated
  as 1989-06-10, 89-06-10, 19890610, 890610, 1989/06/10,
  or 89/06/10.


This is somewhat controversial (in the U.S. anyway).