Visibility on Self-Assessment Total Due Amount Breakdown

I'm wondering whether someone might be able to field this question. I've submitted my self-assessment for 2023-24. I earned less than £6,000 in self-employed income. The bulk of my income is from PAYE, which is taxed at source. My tax bill has been calculated at over £2,000, at almost exactly 40% of the self-employed income. However, my total income from PAYE and self-employment was still under £50,000 - within the 20% tax bracket. I'm curious to know how this figure was calculated, and whether I can access or will receive a more detailed breakdown of the total due amount. I'm not suggesting that it's wrong, but it is a lot higher than I expected, as I anticipated being taxed at 20%. I've tried asking the chatbot, but it seems to only give me answers relating to Child Benefit, which is not applicable, and I have not enquired about.

Hi,
We cannot view your personal records on the forum. Please contact our team for advice on your query:
Self Assessment: general enquiries
Thank you.

I’m well aware that you would not be able to discuss specifics of my personal account. My question for the forum, which does not involve disclosing or discussing personal information, was whether there was a way to view a detailed breakdown of my tax calculation (or if I would be provided with one). As mentioned above, your chat bot is not helpful.

Hi
To give you a detailed explanation as to why your Self Employment income has been taxed at around 40%, as well as to make amendments if any are necessary, please contact us directly by webchat or phone via Self Assessment: general enquiries - along with any advice you might need, we can issue a copy of your tax calculation that should explain the amount of tax requested.