https://forum-narutoen.oasgames.com/page/show-post-34483-1.html

see the last few post in QV's link

but basically it means if week 1 is for local gnw, then week 2 xgnw.. week 3 local gnw, week 4 xgnw, alternating weeks,

so "Lasting 2 week meaning 2 week cooldown. (week 1 and 2 once) (week 3 and 4 once) for example

and it can be used in week 1 and week 3 for local gnw weeks only. (which are actually qualifier rounds for xgnw weeks)

you won't get any extra pack in week 2 and 4 of the month. that's what happen to our group gnw.