Because the cell is formatted as General, Excel perceives the entry to
be an integer number and trims off the leading zero. If you dig the
mm/dd/yy date format, you can use this formula in a new column to parse
the 10298 into an Excel date:

=IF(LEN(A1)=5,LEFT(A1,1)&"/"&MID(A1,2,2)&"/"&RIGHT(A1,2),LEFT(A1,2)&"/"&MID(A1,3,2)&"/"&RIGHT(A1,2))

.... where A1 contains the 10298. This formula checks the length of the
entry and parses accordingly.