Fix comment about minimal length of truncated message

Author: Pierre-Sassoulas

src/_pytest/assertion/truncate.py

@@ -49,13 +49,13 @@ def _truncate_explanation(
     # Check if truncation required
     input_char_count = len("".join(input_lines))
     # The length of the truncation explanation depends on the number of lines
-    # removed but is at least 67 characters:
+    # removed but is at least 68 characters:
     # The real value is
     # 64 (for the base message:
     # '...\n...Full output truncated (1 line hidden), use '-vv' to show")'
     # )
     # + 1 (for plural)
-    # + int(math.log10(len(input_lines) - max_lines)) (number of hidden line)
+    # + int(math.log10(len(input_lines) - max_lines)) (number of hidden line, at least 1)
     # + 3 for the '...' added to the truncated line
     # But if there's more than 100 lines it's very likely that we're going to
     # truncate, so we don't need the exact value using log10.