I think you need to get back with the person that sent the drawing to you. I think the designer intended to have some GDT symbols there, but the internal code that instructs the computer what symbols to show got corrupted. Its like the imbedded characters word processors use to create effects like bold or italics, or for special symbols like the degree symbol. Somehow the code got corrupted and computer that printed the drawing didn't know how to interpret it, so it just printed the characters as they are, instead of the GDT symbols that were the designer's intent.