Time frame for upgrading from Possessory to Absolute Title

I am considering a property which is currently registered with a Possessory Title due to loss of original documents. The property was inherited by a family member and Possessory Title was acquired in Feb 2023. Additional documents were provided but Land Registry did not agree to upgrade to Absolute so the current owner accepted the Possessory Title in Oct 2023.
I want to ascertain if the 12 years waiting period before absolute title can be requested started from first registration, i.e. Feb 2023 and is unaffected by any new sale (therefore Feb 2035), or whether it started in Oct 2023 when it was accepted by the current owner, or whether it would start from scratch if we went ahead and purchased the property this summer (therefore summer 2037).