diff --git a/apps/builder.lua b/apps/builder.lua
index 1d16c19..bc7d14a 100644
--- a/apps/builder.lua
+++ b/apps/builder.lua
@@ -1703,6 +1703,7 @@ function supplyPage:setSupplies(supplies)
     else
       entry.need = entry.need + s.need
     end
+    entry.need = entry.need - turtle.getItemCount(s.index)
   end
 
   self.grid:setValues(t)
diff --git a/sys/apis/util.lua b/sys/apis/util.lua
index 951701c..6dd4a85 100644
--- a/sys/apis/util.lua
+++ b/sys/apis/util.lua
@@ -22,10 +22,10 @@ function Util.tryTimes(attempts, f, ...)
 end
 
 function Util.throttle(fn)
-  local ts = os.time()
+  local ts = os.clock()
   local timeout = .095
   return function(...)
-    local nts = os.time()
+    local nts = os.clock()
     if nts > ts + timeout then
       ts = nts
       os.sleep(0)