If you are cascading the growth percentages from Month to Weeks, you are way off. You don't have to multiply or divide it by anything - just pull the values from Top to bottom. You will have to use LOOKUP while doing so.
If your Jan month shows 1% growth for a Product Family then the expected result is that all 4 weeks of Jan should show 1% growth rate for that particular product family.
Here is the formula that is required to pull the values. I would recommend you understand the formula and the usage of LOOKUP in such cases. Since Anaplan doesn't know how to cascade the values from Month to Weeks, we are asking it to use Whatever values we have at Parent level ( Month Level) in Weeks.
@lcapon it might be that your module or line item has different name, did you check that? In general, try to go to the module and click on the line item instead of typing the formula, it can help you to avoid such errors.