if u put a item inside a factory overlay controller box
go out and u will see a icon on factory
then u can use "long hand inserters" to pick item from factory to a box
u will see that item be transfered to the box and your old item still in controller box in the factory
if u put a item inside a factory overlay controller box go out and u will see a icon on factory then u can use "long hand inserters" to pick item from factory to a box u will see that item be transfered to the box and your old item still in controller box in the factory