how can insert the record in item no series '00001' field, if delete this record

how can insert the record in item no series ‘00001’, if delete this record and again insert that record but it insert into 00002 item no series for example.

insert 20 record save 00001 - 00020, and the record i import is not correct, so i delete the record and again import the record but it save into the item no series 00021-00040.

i want to save from starting no, series. like 00001 - 00020.

Thanks

The system will not do this for you as once you have used the number it is used and the next number to use field is populated in the number series. You can however manually change the last number used, of course if you start posting things you can create a terrible mess.