Sequence Current Value Resetting

Twice a year we import class information into table class. My first
time doing this was with the spring import in August and the import
failed because the Current Value was less than the Max ID in the table.
I changed the Current Value to the Max ID and was able to do the import.
After the import, the new Current Value matched the Max ID and I thought
I had solved my problem. I did not expect any problem today when I when
to do the fall import. I was unable to do the import and discovered
that the Current Value was 156 less than the Max ID. I advanced the
current value to 21557, was able to import 276 rows, and the current
value properly became 21832. Any thoughts as to why this value keeps
"slipping?" Thanks.

Property Value

----- -----

Name tblclass_classid_seq

OID 23937

Owner dbdevel

ACL
(dbdevel=awrdRxt/dbdevel,jboss=arwd/dbdevel)

Current Value 21832

Minimum 1

Maximum 9223372036854775807

Increment 1

Cache 1

Cycled No

System sequence? No

Comment

-- Sequence: tblclass_classid_seq

-- DROP SEQUENCE tblclass_classid_seq;

CREATE SEQUENCE tblclass_classid_seq

INCREMENT 1

MINVALUE 1

MAXVALUE 9223372036854775807

START 21832

CACHE 1;

ALTER TABLE tblclass_classid_seq OWNER TO dbdevel;

GRANT ALL ON TABLE tblclass_classid_seq TO dbdevel;

GRANT SELECT, UPDATE, INSERT, DELETE ON TABLE tblclass_classid_seq TO
jboss;