Yes those words are clear, the issues is that russia is claiming the agreement was with the last government of Ukraine, which no longer exists as it was dissolved and recreated during their coup detat. Since the agreement is not very explicit that is entierly open to interpretation. Obviously I would disagree with Russia and would fin them in the wrong even if they had no treaty anyway. But by signing a treaty that is so sparse in its wording it does leave things open to reader interpritation.