Hi @chandra
We're glad you're here. When you get a chance, please introduce yourself on this forum thread. I'd also encourage you to add a real picture as your avatar because it helps build community!
Such a sheet shouldn't be edited manually. You should remove those changes.
That might be caused by changed formatting (it probably happened when you edited the sheet manually), please try to select the broken column and play with different formats (it's in Format -> Number) like Plain text or Date/DateTime.