Hi
Period which you see in ck24 refers to the period for which future price (which comes after marking) is available. Press F1 help and see the note there. It is not that you are releasing cost for this period.
Usually when you release cost in the period it is valid for all the period which are covered in the range of periods you have given at the start i.e 'date from' and 'date to'. Cost is valid upto the period given in 'Period to' at this step.
Regards
Rajneesh Saxena