This is done by utilizing the roll back lag.
1. wait till the item server is lagged or u can lag it urself. by testing with ss or dropping 1a continuesly
2. when u feel that the item server is lagging, start lagging ur internet, with any other programs and such
3. which ur internet is lagging, and the item server is lagging, start running toward any direction.
4. while running, drop an amount of adena on the ground
5. since ur internet is lagging, the server will loop u back
6. but ur item will still remain there, and ur game will continue to loop back and does the same motion.
7. when the item server stopped lagging, your dropped items will be at the exact same spot, and u can pick up multiple of it.