Try this:
// x and y horizone ..
setarray .x_line, 152,155,163;
setarray .y_line, 111,109,106,103,101,99,96,93,91,89;
Add more x or y line if you want more.
and don't forget to add more duplicate npc vend_slot
prontera, 1, 1, 4 duplicate(vend_slot) #vend_slot1 858
For my example, x * y = 30 NPC. So i need to duplicate 30 npc:
Hope this can help you.