Hi,
Thank you for posting query to us.
I have tested the issue by importing a excel sheet to GridControl by GridExcelConverter. But it is exporting formulas to grid cell as shown in excel cell. The formula in grid cell also does not have any quotes in grid cell. Please see the sample that I tested the issue.
http://files.syncfusion.com/support/Grid.Windows/F82345.zipCould you please have a look at the above sample, if still the issue exists please reproduce the issue in the sample or provide us a sample having issue?.
Regards,
Jisha