Total On hand - Sum of unreserved and reserved items in inventory.
Available to transact - Sum of unreserved and soft reserved items in inventory(items against which reservation and scheduling is done but pick confirm not)
Available to transact - Only unreserved quantity

Relationship Total On hand >= Available to transact >= Available to reserve

For the item CM11062
Total Quantity 9582
Available to Transact 9579
Available to Reservable 9574
The difference between available to reserve and available to transact exists because some of the items might be present in a subinventory which is not reservable like stockfloor, from where transactions can be done.
 We 'll put a new SO line of qty 50 and 'll verify the quantities after scheduling

Available to transact and avialbe to reserve is reduced by 50 quantity.
Total Quantity 9582
Available to Transact 9529

Available to Reservable 9524