Username3000

Hello I made c.£1050.00 in ad hoc self employment. I understand I have a trading limit £1000.00. I completed a self assessment and I need to pay tax of approx £350 - I would have thought it would have been just for the amount over the trading allowance no? When I was completing my self assessment should I have only put £50 turnover so to minus the trading allowance. If it’s correct it doesn’t seem fair, so I’m leaning on thinking there’s an error somewhere.