Can someone tell me how to fix the following code please?

SET GENERATOR GEN_NEW_AUTHOR_ID TO (SELECT MAX(AUTHOR_ID) FROM AUTHOR);

I have data that I have migrated from Paradox to InterBase. I am currently
writing a script with all the updates that I am making to the data, as I
will have to go through this process again.

I am trying to create primary key generators that are set to the primary key
value of the last record in the table, but the code above doesn't work.

What is wrong?
Thanks,
Stephen