auto drop is the same as auto equip. it will drop it if your bags are full, put it in your inventory if they are not. plain and simple, dont fill all your slots(....that line seems funny to me

)
anywho, its not that you are dropping it because you are clicking on some place TO drop it, it is that you are dropping it because all of your slots are full(OMG i said it again

) and as soon as one is emptied, you will put them in your inventory.
now i COULD be wrong...all your slots could not be filled and this could be the case, but most of the tradeskill type macs ive written/modded/seen work this way. thats why theres the "sell" part to the macro if you DO have the item. well, that and all your slots will fill up much faster if you didnt sell

:)
---Genoius---