diff --git a/compacting-storage.lua b/compacting-storage.lua
index b3edf3f..889edd9 100644
--- a/compacting-storage.lua
+++ b/compacting-storage.lua
@@ -6,9 +6,10 @@
 
 -- constants
 
-local INVENTORY = ""
+local INVENTORY = "left"
 local SLEEP_TIME = 30
-local AMOUNT_PER = 63 -- the amount of item change per request
+local AMOUNT_USED = 63 -- the amount of item used per request
+local AMOUNT_RETURNED = 7 -- the amount of item returned per request
 local ITEM_TYPES = { "iron", "copper", "zinc", "gold", "electrum" }
 local PRIORITY = { "ingot", "block", "nugget" }
 
@@ -18,11 +19,11 @@ end
 
 -- TODO map targets to specific relays
 local target = {}
-target.iron = peripheral.wrap""
-target.copper = peripheral.wrap""
-target.zinc = peripheral.wrap""
-target.gold = peripheral.wrap""
-target.electrum = peripheral.wrap""
+target.iron = peripheral.wrap"redstone_relay_0"
+target.copper = peripheral.wrap"redstone_relay_1"
+target.zinc = peripheral.wrap"redstone_relay_2"
+target.gold = peripheral.wrap"redstone_relay_3"
+target.electrum = peripheral.wrap"redstone_relay_4"
 
 -- Levels
 local limits = {}
@@ -52,7 +53,7 @@ function sum_items (inv)
     end
     for slot, item in pairs(inv.list()) do
         local type, form = item.name:match".-:(%l-)_(%l*)"
-        if type ~= nil and form ~= nil then
+        if result[type] ~= nil then
             result[type][form] = result[type][form] + item.count
         end
     end
@@ -85,10 +86,11 @@ function drain (type, form, amount)
     elseif form == "ingot" then
         conversion = "ingot_to_block"
     end
+    print("Draining %d %s %ss":format(amount, type, form))
     request_multiple(type, conversion, amount)
 end
 
-function fill (type, form, amount)
+function fill (type, dest, amount)
     local conversion = nil
     if dest == "block" then
         conversion = "ingot_to_block"
@@ -99,6 +101,7 @@ function fill (type, form, amount)
             conversion = "block_to_ingot"
         end
     end
+    print("Converting %d %s %ss to %ss":format(amount, type, src, dest))
     request_multiple(type, conversion, amount)
 end
 
@@ -106,7 +109,7 @@ end
 function should_drain (type, counts)
     local drain_form, amount = nil, 0
     for _, form in ipairs(PRIORITY) do
-        local diff = counts[form] - target[type][form][2]
+        local diff = counts[form] - limits[type][form][2]
         if diff > 0 then
             amount = math.ceil(diff / AMOUNT_PER)
             drain_form = form
@@ -118,7 +121,7 @@ end
 function should_fill (type, counts)
     local fill_dest, fill_src, amount = nil, nil, 0
     for _, form in ipairs(PRIORITY) do
-        local diff = target[type][form][1] - counts[form]
+        local diff = limits[type][form][1] - counts[form]
         if diff > 0 then
             if fill_dest == nil then
                 amount = math.ceil(diff / AMOUNT_PER)