Yes you need to set the dimension group to have item coverage by warehouse to set a safety stock by warehouse.
I do not like maximum - it orders up to that figure. I would suggest you look at period and see what the usage does. If you set a maximum of 80k and you need 200k it will still suggest you purchase/buy 280k
Coverage time fence is how far you look out into the future. If you have a lead time for this item of 5 days why set this to look out 300 - if you have demand in 20, 50 and 100 days it would tell you to order them with an order date of 15, 45 and 95 days from today. Look at your lead time and how far ahead you want to plan or where your demand is.
Set negative and positive days to the coverage time fence for your start to prevent the impact of them. Once you are more comfortable or want to play further with the impact of future demand and the demand coming within the expected order feel free to play with this. In the mean time read blogs like this.
Or this one
