diff --git a/main.go b/main.go
index eb42745..e3c5e01 100644
--- a/main.go
+++ b/main.go
@@ -514,7 +514,7 @@ func analyzeFramePersistence(videoPath string, tolerance uint64, csvOutput strin
 	// SECOND PASS: Calculate real frame times and write CSV
 	if csvWriter != nil {
 		for i, frameData := range frameAnalysisData {
-			realFrameTimeMs := float64(uniqueFrameDurations[frameData.uniqueFrameCount-1]) * frameTimeMs
+			realFrameTimeMs := float64(uniqueFrameDurations[frameData.uniqueFrameCount]) * frameTimeMs
 			err := csvWriter.Write([]string{
 				strconv.Itoa(frameData.frameNumber),
 				fmt.Sprintf("%.2f", frameData.effectiveFPS),