Release to Warehouse Error

Hi, I have set an item "A" with unit sequence group "Ea Box20". 1 Box20 is for 20 ea. Assume we have 3 locations, A1 = 99 ea, A2 = 100 ea, A3 = 100 ea. Now I have a sales order for item "A" with 2 lines with different delivery schedule. Line 1, "A" is gonna be sold for 200 ea on 1-Mar-2015, and line 2, "A" is gonna be sold for 60 ea on 1-Apr-2015. Then I reserve those 2 lines together because of special request. When we release that sales order, AX will raise an error "[item]: XX cannot be reserved because only XX are available in the inventory."

Is something wrong with my setup or it's a bug? Can someone help me?

Thanks.