Multiple Inventory Counts

I need to know if you are supposed to be able to add in count totals into an open Physical Inventory from multiple stations at the same time. We disperse staff throught our store to count items in several storage areas. I then open a physical inventory count and ask staff to open Store Operations, open the physical inventory and add their counts in. However, it appears the when you hit ok it OVERWRITES anything in the count instead of ADDING to it. Is this by design or something wrong with our system.