A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
I think it's just made that way.
If you could hide the cells that you don't want included (A3, A5 etc) then you could base the sparkline on A2:A10 and use the option not to show data in hidden rows. Otherwise I guess you need to make a range containing cells linked to the alternate cells in your original range and build the sparkline from the new range which could be on a hidden sheet.
Bill Manville. Excel MVP, Oxford, England. www.manville.org.uk