In Felt - F Strategy, indices are different for American style and ENHC.
Even in ENHC, if rule is OBO(lose original bet only against dealer black jack), then it shouldn't be different.
If CVDATA consider the time delay of dealer's second card, it is understandable.
Surrender index of 16 against 10 is -6 in American style, -13 in ENHC.
My local stores have different rules. Need to clarify.