The logic of private use adjustment

Dear tutor,

I understand that when computing the tax adjusted trading profit using the cash basis, the use of flat rate expenses should be assumed to apply. But I do not understand why the cash basis private use adjustment is added to the revenue instead of being deducted, as I thought this adjustment is kind of expense and should be deducted.

And how can I understand the logic of private use adjustment correctly when computing taxable profit?

This is an extract of an example of taxable computation using cash basis:
“Calos started trading on 6 April 2023 and has decided to prepare his first set of accounts to 5
April 2024.
Revenue includes £10,275 which is still receivable at 5 April 2024.
…
The cash basis private use adjustment for one occupant in a business premises for a 12 month period is £4,200. ”

Solution:
“Revenue (£48,035 – £6,575) = £41,460
….
Add: Private use adjustment (Note 3) £4,000
Note 3: The private use adjustment of £4,000 relates to the private element of food and utility costs. ”

Thank you!