Within the Statistics Page, you have two view options for multiple choice question types (i.e. checkbox questions). With multiple choice question types respondents can select multiple answers so while you may have 400 respondents a multiple choice question could have many more responses. You can to choose to break your data down by Respondents or Responses.
The default view when you log into your stats page will be by Respondents. When viewing your data by "Respondents", the system will calculate your answer choices to equal 100% of respondents. This percentage reflects the total number of respondents in your survey as shown below.
Similarly, when viewing your data by "Responses", the system will calculate your answer choices to equal 100%. The difference in this calculation is that the percentage reflects the total number of responses (answer choices) selected within the multiple choice question. Whereas the survey was completed by only 400 people but they responses totaled 582 as an individual respondent was able to select multiple answers.
By default, the statistic page will report data in the "Respondent" view.
You can switch to the "Responses" view by selecting the check mark box (shown in the screen shot below) via the View Options tab. Once selected, the statistic page will update and apply this view option across all of the multiple choice questions throughout your survey.
Please don't hesitate to reach out if you have any questions!