The UK CAA have always applied a rather curious approach to this type of situation.
If a candidate has booked a number of exams for a given week, then attends some but not all of them, they will all be classed as attempts. The non-attended exams will be recorded as failures.
But if the same candidate had booked the same exams and attended none at all, then they would not be classed as an attempt, none would be recorded as failures and the exam fees would be returned.
This could of course simply be a peculiarity of the UK CAA. they may apply a different approach.