Question about Data displayed by SQLplus

I was wondering if anyone else has experienced this and if anyone has any idea of what this could mean:

We have a process which calculates summary information and writes to a certain table. One of the columns of this table is datatype numeric. When we use sqlplus to querry this table, we'll occasionally find that the value in the this column is :000
We have absolutely no idea how this value is getting into this column (it is not within the scope of our application) and we've not been able to manually insert a value like this.
Does anyone have any clue whatsoever what this value could indicate? Please respond by email. Make sure to remove the 'nospam' from the return address. Received on Tue Mar 03 1998 - 00:00:00 CST