diff --git a/discovery/manager.go b/discovery/manager.go
index 1bc952fee2..a8d556a75d 100644
--- a/discovery/manager.go
+++ b/discovery/manager.go
@@ -74,7 +74,8 @@ type Manager struct {
 	logger         log.Logger
 	actionCh       chan func(context.Context)
 	discoverCancel []context.CancelFunc
-	// We use map[string]*targetgroup.Group to handle Discoverers that send only updates instead of all targets on every update.
+	// Some Discoverers(eg. k8s) send only the updates for a given target group
+	// so we use map[tg.Source]*targetgroup.Group to  know which group to update.
 	targets map[poolKey]map[string]*targetgroup.Group
 	// The sync channels sends the updates in map[targetSetName] where targetSetName is the job value from the scrape config.
 	syncCh chan map[string][]*targetgroup.Group