I'm not sure of the rules, but a year is an awfully long time for such a basic level of information to be retained.

In general only the instructor you did the DSD (the non-certification 1/2 day experience) can recognise it when taking you on to a certification course. In any case, whether or not the DSD is credited is at the discretion of the instructor doing the certification course.

I'm not absolutely sure of the details and I await Elbert's correction!