The number of total responses count is different than tabulated response.
After further technical investigation, I found that when a user responds to a survey, it is necessary for him to click on Finish at the end of the survey to complete the response.
If a user does not click on Finish, the response is not completed, but the incomplete response is saved anyway:
The number of responses is updated in the view Overview of the survey
In addition, the response does not appear in the view Graphical Summary of the survey.
In the view All Responses of the survey, the response is visible only to the user who began to respond. Others users only see the completed responses.
Only the user who began to response can solve this issue. Other users (including users with "Full Control" permissions, the owners of the TeamPlace and even the administrators of the TeamPlace servers) cannot solve it as they can't show the incomplete responses.
This user has to go the view All Responses of the survey, to find the response that is not completed, and to select Edit Response in the drop-down menu.
Then the user has to complete the response and to click on Finish at the end of the survey.
This is a by design behavior.