Long callback fired again when it stoped

Dash Python
1 
@app.long_callback(

    output=Output('refresh_btn', 'n_clicks'),
    inputs=[Input('clean_raw_data_button', 'n_clicks'),
            State('userid', 'data'),
            State('refresh_btn', 'n_clicks'),
            State('file_list_completedata', 'value')
            ],

    running=[(Output('clean_raw_data_button', 'disabled'), True, False),
             (Output('clean_raw_data_button', 'children'), 'wait for processing', 'Clean the selected data')],
    prevent_initial_call=True
)
def clean_raw_date(n2, userid, n1, files):
    print(n2, n1, files)
    for file in files:
        raw_data_cleaning(userid, file)
    if n1 != None:
        return n1 + 1
    else:
        return 1

I got this result
1 None
1 1
1 2
1 3
1 4
1 5
1 6