From a book called Access 2013: The Missing Manual:
However, there may be times when you need to share your data with people who are using truly ancient copies of Access. Versions before Access 2007 use a different database format, called .mdb (which stands for "Microsoft database"). And, as you can see in Figure 1-14, the .mdb format actually comes in two versions: a really, really old version that supports Access 2000, and an improved that Microsoft introduced with Access 2002 and reused for Access 2003.
As you can see, it really should be an improved version or at very least an improved one. So, why do you think the author has left them out? You think that's because he wanted to make that part sound a little bit terser for the purpose of a nicer grammar flow? Would you do the same if you had to write that sentence?