first time pass is everything is passed i.e all items and you are awarded IR priviliges.
first series pass is failed 1 or more (but less than 5) individual items on first attempt but passed tham all at the 2nd attempt. Sometimes called a partial pass.
If anyone of these items is failed again at the 2nd attempt then the whole test has to be taken again as opposed to just individual items.
You are allowed to fail no more than 5 individual items on the first attempt else you have to sit the whole test again.