1 year gap between 2 years study - is this a problem ?

I am currently studying in Australia (doing a graduate diploma) and have question about my visa options and eligibility. This is my background:

I came to Australia in January 2006 and did a 1 year Masters .

In 2007 I was doing a PhD (which I quit).

Beginning of 2008 I started graduate diploma on subject very closely related to my Masters . I will complete this in December.

I would like to apply for permanent residency, but my nominated occupation is only 50 points so I do not have enough for PR.
So I would like to apply for the temporary graduate visa first (485) and then PR once I have one years work experience.
I am worried that for the 485 visa the 2 year study requirement states "you must have completed in no less than 16 calendar months....
more than one qualification resulting in a total period of at least two (2) academic years study".
I had basically had a one year gap between my two years of study (since I did not complete the PhD it just looks like a gap).
How does this affect my eligibility to satisfy the 2 year requirement? Also I don't quite understand the part about the 16 calendar months in general - what does that mean exactly. Any help would be much appreciated. Thanks very much! Anna