Hi everyone, i would like to enquire matters relating to the corporate tax computation. i have some questions as per below:

              Profit after tax                     xxx
(less)      Non-business income           (xxx)       <---- the result will give you profit generated from business income
add         Non-allowance expenses      xxx          <---- This is deducted because there are some profits that are non-deductible being deducted at the profit after tax level.
(less)      Special deduction                (xxx)        <----[[/I]U]i dont quite understand this (why do we need to deduct since all expenses has been deducted at the profit after tax level.[/U] (Special deduction are some expenses which generally non-taxable(has to add back) but deemed taxable/deductible by government to encourage spending on that kind of expenditure, i.e. secretarial fees.)
(less)      Double deduction                (xxx)        <--- i dont understand this as well. (A double deduction means you can deduct twice on the expense you made in related to certain expenditure, the DD is determined by government to encourage spendings on that particular sector, i.e. renewable energy.)
[I]
=           Adjusted income                 xxx
Can someone explain this to me? i would like to learn this tax computation well. However, i dont quite understand.

Or is there any sites/ platform available for me to understand better?

THank you !!!!!!!