Firstly, I have read "Low-inventory-level fee further explained" which didn't explain any of this

I am just trying to work out how much i will be looted by Amazon with their new "low inventory surcharge" but i really can't get my head around this part. The fee charged is calculated "at the parent product level"

"So all the child/variations will have the same historical days of supply."

Say i have one product which has multiple colours and sizes

I might have 100 variations on one listing. How on earth is ONE figure for days of supply arrived at?

If 99 products are at the 90 day minimum stock level, but 1 product is at zero stock how does that affect the number?

Will i be charged low inventory surcharge on all sales from the asin because of one out of stock child?

Another example, I might have a colorway that less 5 times less frequently than the most popular colorway.

Do i need to keep this colorway as well stocked as the other ones since they share the same supply figure?

I get product made in china and ship it to the US but i am not based in the US (unfortunately)

Its becoming impossible to make this work without physically being in the US and drip feeding stock every few days to FBA My latest FBA shipment just arrived but the listing already says its too low stock because its reading from christmas sales numbers whereas we are now in the new year and sales are dead. If i was to send in more I would be charged long term storage costs in a few weeks.

I need a proper explanation on how this admin heavy fee is going to work