Grace period and prorata calculation in membership plan

I have setup a membership plan one year duration and fixed expiry date. I have used prorated cost by months for persons joining before the expiry date and a grace period of 30 days where persons joining in this period before expiry would have an extra 12 months added to their expiry date. My problem is that persons joining in the grace period get 12 months added to their expiry date (which is good) but they are only charged the prorata calculation to the first expiry date. i.e. Someone joining 1 day before the expiry date would be charged pro rata almost nothing and get the next 12 months membership for free. I am very new to membership pro so please forgive me if I have missed something obvious.
Thank you,
Noel Adams

Hi Noel

It's hard to understand the issue without checking the plan you setup. Could you please submit a support ticket sending us:

- Super admin account of the site
- Tell me ID the subscription plan
- Tell me ID of the subscription record which has this wrong amount and end date

I will check the data to see what's wrong and find a solution

Tuan