All Axi Index contracts are based on a relevant Futures exchange price. Futures contracts have an expiry date that can be several months ahead and those forward prices can be higher or lower than the cash price, depending on market conditions.
In order to avoid the risks of final day volatility, Axi rolls over contracts one trading day prior to the exchange expiry.

For example, when the Australian SPI contract expires in March, the price rolls over to the next quarterly price (June). Because of this, the price displayed on the MT4 platform is likely to increase or decrease, dependent on the value of the June contract relative to the March contract. This does not represent an actual price increase or decrease, simply a movement to a new reference point. As such, traders will incur no profit or loss when rolling over to a new contract except for the spread.
In order to ensure clients are not adversely affected, Axi will simply make any necessary cash adjustments. You can check CFD Contract Rollover Dates here.