you dates dont quite make sense in column J

they are just weeks
but the first starts on a friday and others on a saturday - is that a typo

those dates can be created automatically but how will excel know when to start the week?
can it be based from column B perhaps look at the minimum date and choose the saturday before that

Then looking at your count - is that using the info from B and C
the item with 7
you dont have 7 items that started after 26/3/2015

row 8,9,10 & 11 starts after 26/3/15 so thats a max of 4
and none closed in that week - so still 4

what am i missing on the counts