I suspect the original poster is referring to Civil Code Section 2942.1:
2954.1. No lender or person who purchases obligations secured by real property, or any agent of such lender or person, who maintains an impound, trust, or other type of account for the payment of taxes and assessments on real property, insurance premiums, or other purposes relating to such property shall do any of the following:
(a) Require the borrower or vendee to deposit in such account in any month an amount in excess of that which would be permitted in connection with a federally related mortgage loan pursuant to Section 10 of the Real Estate Settlement Procedures Act of 1974 (12 U.S.C.2609), as amended.
(b) Require the sums maintained in such account to exceed at any time the amount or amounts reasonably necessary to pay such obligations as they become due. Any sum held in excess of the reasonable amount shall be refunded within 30 days unless the parties mutually agree to the contrary. Such an agreement may be rescinded
at any time by any party.
(c) Make payments from the account in a manner so as to cause any policy of insurance to be canceled or so as to cause property taxes or other similar payments to become delinquent.
Nothing contained herein shall prohibit requiring additional
amounts to be paid into an impound account in order to recover any
deficiency which may exist in the account.
Any person harmed by a violation of this section shall be entitled
to sue to recover his or her damages or for injunctive relief; but
such violation shall not otherwise affect the validity of the loan or
sale.
I think the poster is having understandable problems reconciling the requirement of (a) versus (b). I think is could be read that (b) does not allow a cushion.