diff --git a/app/Services/WgTraffic.php b/app/Services/WgTraffic.php
index ce3f6d1..08c9892 100644
--- a/app/Services/WgTraffic.php
+++ b/app/Services/WgTraffic.php
@@ -42,7 +42,7 @@ class WgTraffic
                 $idx = (int) floor(($t - $from) / $width);
                 if ($idx >= 0 && $idx < $buckets) {
                     $down[$idx] += $dRx;
-                    $up[$idx] += (int) $r->tx;
+                    $up[$idx] += $dTx;
                 }
             }
             $prev[$pk] = ['rx' => (int) $r->rx, 'tx' => (int) $r->tx];
diff --git a/tests/Feature/WgTrafficTest.php b/tests/Feature/WgTrafficTest.php
index 983f221..8ce4465 100644
--- a/tests/Feature/WgTrafficTest.php
+++ b/tests/Feature/WgTrafficTest.php
@@ -37,8 +37,10 @@ class WgTrafficTest extends TestCase
         $this->sample('B', 50, 5, 600);
 
         $s = app(WgTraffic::class)->series(3600, 6);
+        // Both directions are THROUGHPUT (sum of positive per-peer deltas), not raw counters:
+        // down = A(100+200)+B(50) = 350 ; up = A(10+20)+B(5) = 35.
         $this->assertSame(350, $s['total_down']);
-        $this->assertSame(45, $s['total_up']);
+        $this->assertSame(35, $s['total_up']);
         $this->assertGreaterThan(0, $s['peak_down']);
     }