If you pass first time, you pass first time at series one and all's well with the world. If you get a partial pass at first attempt and later resit the partial and pass, it's still a series one pass. Partial passes are quite common and nowt to be ashamed of.
However, if you fail that first partial pass, you have to retake the whole skill test and this becomes series two.
So you can imagine series three ain't going to look too good on a CV.
Cheers
Whirls