Balance close in accrual plan

Content

Hi Team

I have 2 absence accrual plans, a Personal Leave Plan and a Annual Leave Plan. 

Both have the same configuration ( No transfer of balances, no final disbursement, no disc disbursement, no donations)

Suppose an employee having positive balance for both plans is terminated, i see that the balance for Annual leave remains as is and the balance for Personal Plan is reduced to 0, saying Balance close. 

So I want to know under what situations does the plan say Balance close?