-2 appearing in assignment number

Summary:

We have observed -2 at the end of the assignment number of a rehired employee. There are total 4 record in total out of which only 1 is active.

Example :

1. Pending worker - Inactive ( Assignment Number : P1234)
2. Employee - Inactive ( Assignment Number : E1234 ) - Terminated
3. Pending worker - Inactive ( Assignment Number : P1234-2) - Rehired the same pending worker again
4. Employee - Active ( Assignment Number : E1234-2 )

Why -2 has appeared ? Is it because we rehired the same employee again ?
How can we remove this -2 in assignment number ? Is it possible to do so?

Please help if someone has faced similar issue.