Hi,
Sorry for the wrong suggestion to use Custom Allocation in my last reply.
I just realised that there was a simple solution to your situation.
Actually, you just have to set up your employee as if she joined your company at 1 Jan 2023, and give her full entitlement of 8 days.
Then in the Carried Over, minus the 1 month entitlement from her, i.e. 8 / 12 = -0.67
i.e.
Earning Policy: Prorated over a year, earned on monthly basis
Earning Start: 1 Jan 2023
Valid From: 1 Feb 2023
Valid Until: 31 Dec 2023
Entitled: 8
Carried Over: -0.67
You may check here for more details: Set Up Partial Entitlement