Total units made by week number with varying manufacturing periods

I am trying to calculate formulaically how many units were made during various weeks where the manufacturing period can longer than a week. Where this occurs, I need to allocate the units made against the appropriate week number. The manufacturing time for each unit varies from site to site but is consistent within a site.

The attached workbook is an example. Grateful for any advice

Do you want the total number of units credited to the finish week? If so, try this in C8 and fill down:

=SUMIF($J$8:$J$37,"<"&$A8+1,$H$8:$H$37)-SUM($C$7:$C7)

Beautiful, and I can see how it works.

Many thanks, your assistance is much appreciated.