Function unknown

Hi guys,

I have a slightly complicated question, I’ll tell you straight away.

In week 1 I have to estimate when my product is ready (kilos) to harvest. When I fill in 14 days in week 1 it means that I will harvest my product in week 3. However, when I fill in that my product is ready in 21 days I want to have those 10 kilos in week 4. I don’t need to know the precise number of the week a rounding is already fine.

What is a good formula to use in the cells under predicted kilos(B1, downwards)? I was thinking of some if formulas but they don’t seem to work.