How to assign a value to a specific dictionary key?

Question

Python

Good day.
Faced a problem when changing the value in the dictionary.
There is a dictionary with this structure

{
  "1": {
    "nonce": 1510009763,
    "A": {
    },
    "B": {
    },
    "C": {
    },
    "D": {
    }
  },
  "5": {
    "nonce": 1510009763,
    "A": {
    },
    "B": {
    },
    "C": {
    },
    "D": {
    }
  },
  "15": {
    "nonce": 1510009763,
    "A": {
    },
    "B": {
    },
    "C": {
    },
    "D": {
    }
  },
}

the value 1,5,15 is the time in minutes

if int(self.exportData[keyFirst]['nonce']) + (int(keyFirst) * 60) <= int(time.time()):
                    self.exportData[keyFirst]['nonce'] = int(time.time())

When this line is executed, for reasons unknown to me, the updated time is assigned to all keys [1][nonce] / [5][nonce].
Please explain why this is happening
python 3.5