useEffect values append instead of update

I am writing a react script where whenever new transport data comes from backend, it should track it and show it in frontend, but the problem is whenever new values arrive from backend, it appends with old state. I am confused how to solve it.

const transportData = [
  [
    {
      type: "metro",
      icon: MetroIcon,
      sessionCount: 0,
      totalGreenhouseGazes: 0,
    },
    {
      type: "bus",
      icon: AutoBusIcon,
      sessionCount: 0,
      totalGreenhouseGazes: 0,
    },
  ],
  [
    {
      type: "run",
      icon: RunIcon,
      sessionCount: 0,
      totalGreenhouseGazes: 0,
    },
    {
      type: "carpool",
      icon: CarpoolIcon,
      sessionCount: 0,
      totalGreenhouseGazes: 0,
    },
  ],
  
  ];

 const [allTransport, setAllTransport] = React.useState([]); <-- this is coming from backend


    //in the format {bike: {sessionCount: 1, totalGreenhouseGazes: 10}
bus: {sessionCount: 0, totalGreenhouseGazes: 12}}

I want to these allTransprt data to update the above transport data

 const [transport, setTransport] = React.useState(transportData);
 
React.useEffect(() => {
    // find the mode of transport of populate its data correctly
    const keys = Object.keys(allTransport || {});

    transport.map((groupOfMode) => {
      groupOfMode.map((mode) => {
        keys.forEach((key) => {
          if (key === mode.type) {
            mode.sessionCount = allTransport[key]?.sessionCount || 0;
            mode.totalGreenhouseGazes =
              allTransport[key]?.totalGreenhouseGazes || 0;
            mode.totalDistance = allTransport[key]?.totalDistance || 0;
            
          }
        });
      });
    });
  }, [allTransport]);

From my code, the allTransport data comes, updates in transportData and looks like this in frontend when allTransport has all four selected values.

In 2nd iteration, when the allTransport data comes, it displays the previous values of transportData and updates the one selected. Like this:

This happened when only the three data were selected. Though the red circle was not the one retrieved from backend, it put the previous value. So I want something that if the value is not retrieved from backend, it should just have original value from transportData.

Any help is appreciated. Thanks!!