ReadCell: Decimal Converter cannot convert from System.Double

No worries - here is someone with a similar issue so hopefully it will shed some light.

Format in Excel file is just used to determine how to DISPLAY data on EXCEL FILE. It doesn’t affect data type in datatable in UiPath.

I guess UiPath recognizes columns as Double when the cell only contains numbers (but if it starts with zero and is followed by another number, UiPath recognizes it as String)