Where a UK national is beneficiary of the Withdrawal Agreement in more than one Member State, then the conditions set out in the Withdrawal Agreement must be met separately in each of the Member States in order to have to the right of residence under the Agreement in them. The rules on the continuity of residence are normally applied in each of the Member States separately.
For example, a UK national is beneficiary of the Withdrawal Agreement in Greece as non-permanent resident and beneficiary of the Withdrawal Agreement in Spain as permanent resident. In this case, the citizen concerned must meet the condition of the continuity of residence in each Member State separately depending on the residence right (non permanent/permanent) he/she has in each Member State, ie for Greece absences not exceeding a total of six months per year or an absence of a maximum of 12 consecutive months for serious reasons and for Spain an absence for a period not exceeding 5 consecutive years.
Especially in cases where the citizen concerned has the right of non-permanent residence under the Withdrawal Agreement in more than one Member State, then he/she should meet the conditions of the continuity of residence in each of them in order to retain his/her right under the Agreement. In this case, as the citizen concerned is likely to have difficulty meeting this condition in more than one Member State at the same time, then he/she will have to decide what steps to take (for example make a decision in which Member State he/she will reside and therefore will meet the conditions of the residence etc.).