sessionTimestampFileName 

Namespace: SynicSugar.MatchMake
Class: MatchMakeManager

public string sessionTimestampFileName = "ss_sessiondata";

Description 

This is the file name to save the session start time. It is stored in Application.persistentDataPath/sessionTimestampFileName+.dat at the end of matchmaking.
This file is not always necessary when reconnection, but having this file improves the accuracy of the sessionTime for the timestamp.
This option is intended for use when multiple applications are launched on the same terminal.

Save the following file. If this file does not exist locally on reconnection, the sessionTimestamp is calculated based on the Session's elapsed time sent by the Host.

using System;
using MemoryPack;
namespace SynicSugar.P2P {
    [MemoryPackable]
    public partial class SessionData
    {
        public string LobbyID { get; set; }
        public DateTime SessionStartTimestamp { get; set; }
        
        [MemoryPackConstructor]
        public SessionData(string lobbyId, DateTime sessionStartTimestamp)
        {
            LobbyID = lobbyId;
            SessionStartTimestamp = sessionStartTimestamp;
        }
    }
}

using UnityEngine;
using SynicSugar.MatchMake;

public class Matchmake : MonoBehaviour {
    private void Start(){
        string localuserName = GetLocalUserName();
        MatchMakeManager.Instance.sessionTimestampFileName = localuserName + "_data";
    }
    ///Processes that return a unique name
    private string GetLocalUserName(){
        string username;
        ///...
        return username; 
    }
}