Pension credit and Carer Allowance

Hi all,

Briefly my mum situation. My mum arrived from Ukraine and apply for Pension Credit in May 2022 and start receiving Pension Credit in June 2022. Also she helping out to look after my disabled 5 year old son. We decided apply online on 28th June for Carer Allowance and application has been approved that from 10th October 2022 she will start receiving Carer Allowance for my son. Also money which has been calculated from 28th June 2022 till 19th September 2022 backdated Carer Allowance she only received only half of money. Also her Pension Credit has bee reduced from £182 per week to £151 per week. She received a letter with detailed backdown why her Pension Credit was reduced. My mum was born on 4th April 1950 72 years old.
This was letter was stating: Your income
Some your income is described as “qualifying income”. This amount that counts towards your savings credit because you are over 65. Your qualifying income is shown by “Q” . “E” shows the income that we have estimated.
Benefits
State pension for My mum. 0.00 “Q”
Carer Allowance for my mum. £69.70 “Q”
Total income. £69.70

Your guarantee credit

Your appropriate amount £221.45
Less income of. £69.70
So your guarantee credit is. £151.75.

Your savings credit

The first £158.47 does not count towards the savings credit. This is savings credit starting point. You are not entitled to savings credit.
This is because your qualifying income is not above £158.47.

My question is why Carers Allowance reduce my mum Pension Credit from £182 to £151.75.

Hope to receive detailed answer.

Many thanks,

Victoria