_historyTableCurrentValueUsed() {
        let indexToUse = this.historyTableIndex;
        if (indexToUse < 0) {
            indexToUse = 0;
        }

        let result;
        if (AutoNumericHelper.isUndefinedOrNullOrEmpty(this.historyTable[indexToUse])) {
            result = '';
        } else {
            result = this.historyTable[indexToUse].value;
        }

        return result;
    }
Return the currently used value from the history table.

@returns {string|number}
@private