I hold an Indian Passport and reside in the UK. I have a valid work visa in the UK till Jan 2017. I have got my Schengen Visa on 24/05/2014 for the first time. The Valid Until date on the visa is 23/08/2014 (90 days). It is a multiple entry visa.
I visited Amsterdam on 24/05/2014 and returned to the UK on 27/05/2014 (4days).
I entered Denmark on 23/08/2014 (which is the Valid Until date on my visa) with the understanding that I can enter the Schengen area and cannot overstay until I cross the 90 days total stay within the 180 days period. Well, I just planned to stay for 3 days. And the immigration officer at entry had the same understanding (I clarified this with him) and he let me in.
On my return on 26/08/2014, the immigration officer at the exit was not convinced with the 90 days in 180 days rule and fined me for overstay since my visa says it is valid upto 23/08/2014. I have just stayed a total of 7 days in the Schengen area and still fined for overstay.
Did I really overstay? Is my understanding of the rule of 90 days within a 180 days period not correct?