The Board largely relied on the language of 35 U.S.C. § 325(e), which specifically states that estoppel is invoked as to “a claim in a patent” that “results in a final written decision.” The patent owner’s complaints of harassment from multiple petitions are best addressed, the Board wrote, by its discretion under Section 325(d) to “take into account whether, and reject the petition or request because, the same or substantially the same prior art or arguments previously were presented to the Office.”