How to solve "Number stored as text" problem with SpreadsheetGear ?

Question

Hello, I've decided to try SpreadsheetGear to generate excel workbooks. But on the very first workbook I've met "Number stored as text" problem.

The problem doesn't go away even if I apply formatting to the cells (I tried to apply formatting before and after setting cell values) like this:

r = worksheet.Cells[1, i, grid.Rows.Count - 1, i];
r.NumberFormat = "0.00";

but with no luck.

Thank you in advance. Hope anyone helps.

UPDATE: It seems it is a bug in SpreadsheetGear, because I apply formatting to the whole column and some cells are formatted and some cells are left with "Number stored as text" warning. I need to note, that the number values are stored as strings. If I store them as double or decimal - there is no problem. But I still think it really looks like a bug.