Hi JAHOUL,
These rates are the benchmark rates for meal allowances for an employee and can be found here:
https://www.gov.uk/hmrc-internal-manuals/employment-income-manual/eim30240.
They are the maximum tax and NIC free amounts that can be paid by employers, who choose to use the system.
An employer can pay expenses higher than these amounts, but the excess should be charged tax and NIC.
If you are self employed, you can claim expenses for meals on overnight business trips.
Plesae have a look here:
BIM47712 - Specific deductions: travel and subsistence: living expenses abroad — foreign trades
Thank you.