diff --git a/compacting-storage.lua b/compacting-storage.lua
index e69c3b0..0c0e604 100644
--- a/compacting-storage.lua
+++ b/compacting-storage.lua
@@ -86,12 +86,14 @@ function drain (type, form, amount)
     elseif form == "ingot" then
         conversion = "ingot_to_block"
     end
+    local num_requests = math.ceil(amount / AMOUNT_USED)
     print(("Draining %d %s %ss"):format(amount, type, form))
-    request_multiple(type, conversion, amount)
+    request_multiple(type, conversion, num_requests)
 end
 
-function fill (type, dest, amount)
+function fill (type, src, dest, amount)
     local conversion = nil
+    local num_requests = math.ceil(amount / AMOUNT_USED)
     if dest == "block" then
         conversion = "ingot_to_block"
     elseif dest == "ingot" then
@@ -99,51 +101,72 @@ function fill (type, dest, amount)
             conversion = "nugget_to_ingot"
         elseif src == "block" then
             conversion = "block_to_ingot"
+            num_requests = math.ceil(amount / AMOUNT_RETURNED)
         end
     end
     print(("Converting %d %s %ss to %ss"):format(amount, type, src, dest))
-    request_multiple(type, conversion, amount)
+    request_multiple(type, conversion, num_requests)
 end
 
 -- making the decision what to do
 function should_drain (type, counts)
-    local drain_form, amount = nil, 0
     for _, form in ipairs(PRIORITY) do
         local diff = counts[form] - limits[type][form][2]
         if diff > 0 then
-            amount = math.ceil(diff / AMOUNT_PER)
-            drain_form = form
-            return drain_form, amount
+            return form, diff
         end
     end
 end
 
 function should_fill (type, counts)
-    local fill_dest, fill_src, amount = nil, nil, 0
+    local fill_dest, fill_src, amount_needed, amount_spare = nil, nil, 0, 0
     for _, form in ipairs(PRIORITY) do
         local diff = limits[type][form][1] - counts[form]
         if diff > 0 then
             if fill_dest == nil then
-                amount = math.ceil(diff / AMOUNT_PER)
                 fill_dest = form
+                amount_needed = diff
             end
         else
             fill_src = form
+            amount_spare = counts[form]
         end
         if fill_src ~= nil and fill_dest ~= nil then break end
     end
-    return fill_dest, fill_src, amount
+    local amount_to_use = do
+        local ratio = AMOUNT_USED / AMOUNT_RETURNED
+        local amount_needed_src = nil
+        if fill_src == "block" then
+            amount_needed_src = amount_needed / ratio
+        else
+            amount_needed_src = amount_needed * ratio
+        end
+        if amount_needed_src < amount_spare then
+            return amount_needed_src
+        else
+            return amount_spare
+        end
+    end
+    return fill_dest, fill_src, amount_to_use
 end
 
 function decide_action (type, counts)
     -- using the levels of each form of the item, decide what to do
     for _, form in ipairs(PRIORITY) do
         local drain_form, drain_amt = should_drain(type, counts)
-        local fill_dest, fill_src, fill_amt
+        local fill_dest, fill_src, fill_amt = should_fill(type, counts)
         if drain_form ~= nil then
             drain(type, form, drain_amt)
         elseif fill_dest ~= nil then
-            fill(type, form, fill_amt)
+            fill(type, fill_src, fill_dest, fill_amt)
+        end
+    end
+end
+
+function print_counts (items)
+    for type, counts in pairs(items) do
+        for form, count in ipairs(counts) do
+            print(("%s %s: %d"):format(type, form, count))
         end
     end
 end
@@ -151,6 +174,7 @@ end
 while true do
     -- 1. Sum items in inventory and organize by item type
     local items = sum_items(peripheral.wrap(INVENTORY))
+    print_counts(items)
 
     -- 2. take one action for each item type per cycle
     for item_type, counts in pairs(items) do