diff --git a/internal/sync/cfi_converter.go b/internal/sync/cfi_converter.go
index 366784d..4a4c141 100644
--- a/internal/sync/cfi_converter.go
+++ b/internal/sync/cfi_converter.go
@@ -1321,9 +1321,16 @@ func countTextChars(n *html.Node) int {
 	return count
 }
 
+// countTextCharsBefore counts the text characters preceding target within
+// its document: preceding siblings at each ancestor level, strictly
+// EXCLUDING target's own subtree (callers add the in-node offset
+// separately). Starting the walk at target itself — or recursing after
+// counting the current node's subtree — would re-count the accumulated
+// document once per ancestor level and multiply the result by the node's
+// depth.
 func countTextCharsBefore(target *html.Node) int {
 	count := 0
-	for c := target; c != nil; c = c.PrevSibling {
+	for c := target.PrevSibling; c != nil; c = c.PrevSibling {
 		count += countTextChars(c)
 	}
 	if target.Parent != nil {