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.