personal allowance

Hello,

Need your help to tackle this question below.

Charles is self-employed, and his tax adjusted trading profit for the year ended
31 December 2017 was £110,400. During the tax year 2017/18 Charles made a gift aid donation of £800 (gross) to a national charity.
Charles has been a member of a registered personal pension scheme since May 2015.
He made a gross contribution of £25,000 in the tax year 2015/16 but has not made any
subsequent contributions.

1. The answer is £6,700.
2. The ANI is calculated as follows:
Personal allowance 11,500
Total income = net income 110,400
Less: Gross gift aid (800)
–––––––
ANI 109,600
Less: Income limit (100,000)
–––––––
Reduction of PA 9,600 × 50% (4,800)
––––––– ––––––
Adjusted PA 6,700.

3. Could you explain why £25,000 has not been deducted from the trading income?

Thanks.