diff --git a/sdk/trace/batch_span_processor.go b/sdk/trace/batch_span_processor.go
index 6966ed861..b6e93dea0 100644
--- a/sdk/trace/batch_span_processor.go
+++ b/sdk/trace/batch_span_processor.go
@@ -18,8 +18,10 @@ import (
 
 // Defaults for BatchSpanProcessorOptions.
 const (
-	DefaultMaxQueueSize       = 2048
-	DefaultScheduleDelay      = 5000
+	DefaultMaxQueueSize = 2048
+	// DefaultScheduleDelay is the delay interval between two consecutive exports, in milliseconds.
+	DefaultScheduleDelay = 5000
+	// DefaultExportTimeout is the duration after which an export is cancelled, in milliseconds.
 	DefaultExportTimeout      = 30000
 	DefaultMaxExportBatchSize = 512
 )