If you need to update the table, then the question is: what rules do apply?

The table is already defined as requested ("IsValidSap (should have null defined when adding to the table)") so there's nothing to do with this part.

Therefore, there's no need to update (= alter) the table (definition).

It might be to fill the new column with values based on certain (unknown) requirements.

If the application still runs without any error, I would leave it as it is. In case it fails, it might be due to a bad coding habit of not referencing all column names in an insert statement. In such a case address it to the App Dev team.

Whoever request you to finish this task should describe what's expected. If this can't be done, the implementation of the "requirement" should be postponed until clarification is available.