perfmon: Fix comment

Change-Id: I037c7220941364224a33e1ed082bcde87cbbf57e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/173800
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: David Neto <dneto@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/tools/src/bench/bench.go b/tools/src/bench/bench.go
index a618884..47776c5 100644
--- a/tools/src/bench/bench.go
+++ b/tools/src/bench/bench.go
@@ -206,9 +206,9 @@
 	TestName           string
 	Delta              time.Duration // Δ (A → B)
 	PercentChangeAB    float64       // % (A → B)
-	PercentChangeBA    float64       // % (A → B)
+	PercentChangeBA    float64       // % (B → A)
 	MultiplierChangeAB float64       // × (A → B)
-	MultiplierChangeBA float64       // × (A → B)
+	MultiplierChangeBA float64       // × (B → A)
 	TimeA              time.Duration // A
 	TimeB              time.Duration // B
 }