The cell contains the following data in OOXML: <f>SUM(1,2,3)</f> - The formula <v>6</v> - the calculated value The formula value is imported, but the calculated value is skipped. The feature will be useful if Manual calculation option is supported: https://feedback.telerik.com/Project/184/Feedback/Details/191275-spreadsheet-add-support-for-different-calculation-options-automatic-or-manual