Firebase Notification duplicated message

I am facing a serious issue, I am receiving multiple push notifications. I found it generated lots of registration token. These token were made by the same one person, use same desktop, on same network domain.I have try to send test message to those tokens.And those tokens work.

/* 1 */
{
    "_id" : ObjectId("5ab330e1a8dbc4623df77853"),
    "token" : "d8DtmhvF4_c:APA91bEaGFkn-g2B0-dpOIxfgrvfVbXiB-mLiRPaVfQpGlo4vSYC_FHJfnyQWzLnYmU9CWHqpX1rx1nR7YM7msd5umooOXPXS3dHY9QdQl0NlIkdJ8HQJth1NKPTMy7DhV9HPFrBDQvm",
    "agent" : "mozilla/5.0 (windows nt 6.1; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/65.0.3325.181 safari/537.36",
    "status" : "enable",
    "session" : "89196faa-df82-1e0f-b36b-2854ed3c7b95",
    "time" : "2018-03-22 12:28:17"
}

/* 2 */
{
    "_id" : ObjectId("5ab9b593403ab4ac0f777a63"),
    "token" : "fu-CQUJz8VA:APA91bEn0L-U14Nz0x9nw-Ck3UXbT6CeXpYJZTFBPYCfRH3eGyez3__O6GzA_isY_M_tJiKgofIXrrfhc66tBtiv1ffZ34kuQTe8Qh8oDg43zNo1HSJbQebR1WuMm3P7i28RROTaUpC2",
    "agent" : "mozilla/5.0 (windows nt 6.1; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/65.0.3325.181 safari/537.36",
    "session" : "89196faa-df82-1e0f-b36b-2854ed3c7b95",
    "status" : "enable",
    "time" : "2018-03-27 11:08:03"
}

/* 3 */
{
    "_id" : ObjectId("5abc6b6ebf33dee27bc0ccd5"),
    "token" : "d8DtmhvF4_c:APA91bFUSmTLhe5RHwPBkpUIZCsqzxBjH7yf6HBcmj709xZVG8LaJ07XZTbIZrumb2rKXJ_V9IM6ez6rSKuZqT6iuwRScNEzNQ_CS3Kvcwgp4xrf2VHkYVF5uW7gzF3tq7_izdxwYvvl",
    "agent" : "mozilla/5.0 (windows nt 6.1; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/65.0.3325.181 safari/537.36",
    "status" : "enable",
    "session" : "89196faa-df82-1e0f-b36b-2854ed3c7b95",
    "time" : "2018-03-29 12:28:30"
}

/* 4 */
{
    "_id" : ObjectId("5acab503a94c4152379c6983"),
    "token" : "d8DtmhvF4_c:APA91bFKKQox-DMLej4Mf2zdUfpE3MR0ew48i7lJ-iX7mMskp4KhCJPIhzYsTH88YZXC2FhkLJuUBOsa086Z5OLZ-jU0XFRJz4i2BJI5gWxVa5Npkd5fLsWo4t2nBTdNOZra0SD0gdXb",
    "agent" : "mozilla/5.0 (windows nt 6.1; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/65.0.3325.181 safari/537.36",
    "status" : "enable",
    "session" : "89196faa-df82-1e0f-b36b-2854ed3c7b95",
    "time" : "2018-04-09 08:34:11"
}

/* 5 */
{
    "_id" : ObjectId("5ad3efbeb98df3232dfc7fb3"),
    "token" : "d8DtmhvF4_c:APA91bHsynAV6riwAF4statZxwMt5YJUN19zCd44HRoxp9AOoLwCTG4yrq-aX5UA7ik1UB2H5l30GIYXSqaAqcOYQwyio4jMZF7-SeJ-KR6_LtqlIVNQOuRrvWpW5EAnjWyyhrX3A3rh",
    "agent" : "mozilla/5.0 (windows nt 6.1; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/65.0.3325.181 safari/537.36",
    "status" : "enable",
    "session" : "89196faa-df82-1e0f-b36b-2854ed3c7b95",
    "time" : "2018-04-16 08:35:10"
}

Any suggestion will be helpful for me?