thank you Google!

From April 10 2012 to my EDD June 01 2013 is 59 weeks. Which is 13.57 months. Why they're asking me from the 5th of may is beyond me now.
From April 10 2012 to my end work date of February 13 2013 is 44 weeks. 10.12 Months.

BUT they're asking from May 5.

So, from May 5 2012 to my end work date Feb 13 2013 only works out to be 9.43 months.

Basically I need to be due 2 weeks earlier than I am in order for my first months work to 'count'.
May 1st I could understand as that is 13 months - but May 5th - yes no idea.