ATP balance qty

Hello,

If we create a sales order for 30 kg and ATP qty=100, then we have 30 kg confiremd qty in sales order.

1) I need to know what happens to ATP qty before the sales order is saved and after the sales order is saved. where can we see the behaviour of ATP qty before and after sales order save.

2) How to see the balance ATP qty in system ?

regards

Pamela