Thank you for your report. I confirm this is an issue with the present version of the Kendo UI Spreadsheet. In addition, I have updated your Telerik points for gratitude for bringing the problem to our attention.
I have logged this issue for fixing, and you can track its progress in GitHub:
Apologies for the inconvenience this might caused you.
Let me know if you need additional assistance.
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI