AfterMarketOpen scheduled event error for futures?

AfterMarketOpen scheduled events for futures seems to use stocks regular trading hours as reference. The scheduled event in the example below triggers at 09:20, instead of the expected 17:50. Why is that and any way to come around it without scheduling an event for 17:50 ?

       # Add futures
        tickers = [
            Futures.Indices.SP500EMini
        ]

        self.selected_symbols = []
        for ticker in tickers:
            future = self.AddFuture(
                ticker=ticker, 
                resolution=self.resolution, 
                dataMappingMode=DataMappingMode.OpenInterestAnnual, # Changes when any contracts of next year have a higher volume than the current
                dataNormalizationMode=DataNormalizationMode.BackwardsPanamaCanal, # New contract has true price
                contractDepthOffset=0, # Choose the front month
            )

            self.selected_symbols.append(future.Symbol)
      

        # Scheduled event to allow trades when market re-opens
        self.Schedule.On(
            self.DateRules.EveryDay(self.selected_symbols[0]),
            self.TimeRules.AfterMarketOpen(self.selected_symbols[0], -10),
            self.StartOfSession
        )
        
        
    '''
        Start of session scheduled event
    '''
    def StartOfSession(self):
        self.end_of_session = False