Product feeds import
Try Convert Excel Data Types in the corresponding column. 

Excel 2010


Click the File tab, Click Excel Options, Click Advanced.
In the Editing Options, verify that the AllowEditing directly in cells check box is selected. Click OK.
Double-click the cell you want to format, and then press ENTER.
Click the error button next to the cell, and then click Convert to Number on the shortcut menu


How to convert text to numbers in Excel