Peace be upon you. The essence of remembrance in tasbih is obligatory, which does not contradict the fact that choosing a specific type of remembrance can be recommended. Therefore, a person can perform the remembrance as an obligation while intending the specific remembrance as a recommendation. This is similar to someone who has an obligation, such as making up a missed prayer, and chooses to do so in the mosque because it is recommended. May you be successful in all good.