AKI means the Anti Knocking Index or the Road octane number which is based on the Research Octane number (RON) and Motor Octane Number (MON).

AKI = RON + MON / 2

RON correlates to anti knock performance under mild operating conditions.
MON correlates to anti knock performance under severe operating conditions.

Different Grades of Gasoline
At present world wide three grades of gasoline are generally used.