refactor: update estimated time to head calc

Author: Monika-Bitfly

backend/pkg/blobindexer/blobindexer.go

@@ -126,7 +126,7 @@ func (bi *BlobIndexer) index() error {
 		return err
 	}
 
-	if err := bi.validateSpec(spec); err != nil {
+	if err := validateSpec(spec); err != nil {
 		return err
 	}
 
@@ -349,7 +349,7 @@ func (bi *BlobIndexer) fetchBlockHeader(blockID string, header *constypes.Standa
 	return nil
 }
 
-func (bi *BlobIndexer) validateSpec(spec *constypes.StandardSpecResponse) error {
+func validateSpec(spec *constypes.StandardSpecResponse) error {
 	if spec.Data.DenebForkEpoch == nil {
 		return fmt.Errorf("DENEB_FORK_EPOCH not set in spec")
 	}
@@ -505,7 +505,7 @@ func calculateEstimatedTimeToHeadDuration(estimatedTimeToHead float64) time.Dura
 }
 
 func calculateEstimatedTimeToHead(headHeader *constypes.StandardBeaconHeaderResponse, batchStart uint64, slotsPerSecond float64) float64 {
-	estimatedTimeToHead := float64(headHeader.Data.Header.Message.Slot-batchStart) / slotsPerSecond
+	estimatedTimeToHead := float64(headHeader.Data.Header.Message.Slot) - float64(batchStart)/slotsPerSecond
 	return estimatedTimeToHead
 }