Query on CAP Exempt duration calculation

My H1B petition was approved for Dec’11 to Feb’13 from employer X. Now my petition and visa both expired. I was in USA for 5 month and came back India in Dec’12.

I have a query on CAP Exempt duration -

Is calculation done from the date petition validity started i.e Dec- 2011 Or from the date I last stayed in USA i.e Dec’12 Or the date I entered in USA May -2011

Thanks in Advance…!

I have a similar query
My visa expired in 2008 and i went back to india in 2008. Now i would like to apply for the remaining 5 years left on my visa in 2017 after 9 years. Is it possible ?
I have seen conflicting answers like these mentioned below

Please some one with similar case answer to resolve this confusion. Its very time critical.