Is it permissible to change the intention regarding the number of rak'ahs of continuous Sunnah prayers during the prayer, such as the Sunnah prayer before Dhuhr and Witr?

Changing the intention in the Witr prayer is explained in Fatwa No. 103812. As for changing the intention in an absolute supererogatory prayer, whether by increasing or decreasing, it is permissible. However, for non-absolute supererogatory prayers, such as the regular sunnah prayers (rawātib), the Shāfiʿīs do not permit increasing or decreasing what was intended. The Mālikīs are of the view that it is preferable for someone who intended to pray four rakʿahs of supererogatory prayer to make them two rakʿahs. We have not found an explicit statement from the Ḥanbalīs on this issue, but it may be understood from their statements that it is permissible to exceed the intended number in supererogatory prayers if it is done in a permissible manner. The more cautious approach for someone who has intended a specific number of rakʿahs in a regular sunnah prayer is not to increase or decrease from it.