A place that is Unattended will show with a grey pin. It means that you provided a photo that did not have embedded GPS data so we cannot verify that you were at that place at that time.
If the photo is old or lacks EXIF data for some reason, you can still upload it, but it will appear with a grey pin and will be annotated with "Unattended".
Sample pin popup status:
✖ Unattended (Photo with No GPS data)
✓ Attended (Photo With GPS data)