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Just to clarify, you would like to add or sum up specific values from different submissions and display it on the HTML report? Unfortunately that is not possible, but it can be somehow done in the Visual Report Builder, you can check this guide: https://www.jotform.com/help/187-How-to-Create-a-Visual-Report-with-Your-Form-Submissions
Another way is to integrate your form to Google Spreadsheets, after that, you can use different functions to specifically sum up or create calculations based on the answers or inputs from different fields you have: https://www.jotform.com/help/228-How-to-Integrate-Form-with-Google-Spreadsheet.
The Google spreadsheet can then be embedded or shared to your users so that they can view it, should be somehow similar to the HTML table, there you can create graphs, charts, table that would represent the number of inputs and items on your submissions in totality. Here's a short article about that functionality: https://support.google.com/docs/answer/63728?co=GENIE.Platform%3DDesktop&hl=en
I hope that helps.