Okla. Stat. tit. 84, § 84-226: Expressed value of advancement governs

If the value of the estate so advanced is expressed in the

conveyance, or in the charge thereof made by the decedent, or in the

acknowledgment of the party receiving it, it must be held as of that

value in the division and distribution of the estate; otherwise it

must be estimated according to its value when given, as nearly as

the same can be ascertained.