Mont. Code Ann. § 28-1-1212

All objections to the mode of an offer of performance that the creditor has an opportunity to state at the time to the person making the offer and that could then be made unnecessary by the person are waived by the creditor if not then stated. If the objection is to the amount of money, the terms of the instrument, or the amount or kind of property offered, the creditor shall specify the amount, terms, or kind that the creditor requires.