This is where you indicate to which items the selected item on the left applies. The example above shows what the OASI applies to, i.e. all salary items subject to OASI.
"Applied to" is the mirror image of "Subject to".
If you create a new insurance, you will check all the salary elements on which it will be calculated. The mirroring will be done automatically in the salary elements which will then be Subject to this item.
The mnemonic trick to remember which way it works is :
The salary is subject to OASI.
The OASI is applied to the salary