Hi Sandeep,
Could you share what your Marketing App version is?
Mine is 9.1.0000.8031.
Your contact might had opened his/her marketing email for several times in a minute.

And there is a interface in Marketing developer guide which could give us details of each click for specific contact, you will see Timestamp are actually different for every retrieved records.
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/marketing/developer/retrieve-interactions-contact
Below is my retrieving code:
var url = "https://org.crm.dynamics.com/api/data/v9.0/msdyncrm_LoadInteractionsPublic";
var data = {
"InteractionType": "EmailOpened",
"ContactId": "ec595a43-a3d2-e911-a825-000d3a3b10ec"
};
var req = new XMLHttpRequest();
req.open("POST", url, false);
req.setRequestHeader("Accept", "application/json");
req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
req.setRequestHeader("OData-MaxVersion", "4.0");
req.setRequestHeader("OData-Version", "4.0");
req.setRequestHeader("Prefer", "odata.include-annotations=*");
req.send(JSON.stringify(data));
if (req.readyState === 4) {
if (req.status === 200) {
var results = JSON.parse(req.response)["Data"];
} else {
console.log("err");
}
}
Result for all Timestamps in each interaction for specific contact:
(It seems that the Timezone for retrieving action is different from system time zone or customer journey time zone, but you could try open Email once for test, and there shall be just one record generated.)

Hope it helps.
Best Regards,
Leo