Dispute Number is jumping

Hi,

When i am creating Disputes via Advanced collections, Dispute numbering is jumping by 1000

Disputes are created with below number:-

1000

2000

3000

4000....... 10000

When the last the dispute number was at 10000, i had executed the below script

alter sequence IEX.IEX_DISPUTES_S nocache;

Commit;

Now the dispute numbers are created as below:-

10001

10002

10004

10005

12000

12001

12002

12003

13000

13001

13002

14001

14002

15001

16001

16002

Does anybody has any idea as to why still the Dispute numbering is jumping

Regards,

Arvind