Amendment and compliance check

Hello, I have a question concerning the income tax administration. It is from ACCA study hub.
For the tax year 2021-22, Willard filed a paper self-assessment tax return on 10 August 2022.
What is the deadline for Willard to make an amendment to his tax return for the tax year 2021-22, and by what date will HM Revenue and Customs have to notify Willard if they intend to carry out a compliance check into this return?

Amendment Compliance check
A 10 August 2023 31 January 2024
B 10 August 2023 10 August 2023
C 31 January 2024 10 August 2023
D 31 January 2024 31 January 2024

The correct answer is C
Explanation:
Amendment – 31 January 2024. Willard can make an amendment within 12 months of the prescribed filing date.

Compliance check – 10 August 2023. HMRC can initiate a compliance check within 12 months of the actual filing date.

However, I understood from ACCA study hub that,
“Individual taxpayers can amend their tax return at any time within the 12 months following the prescribed filing date”
As Willard filed a paper tax return, shouldn’t it be 31/10/2023?
Thank you very much.