How did the Prophet, peace and blessings be upon him, extend each of "Bismi Allah Ar-Rahman Ar-Rahim," and how many vowel counts did he extend in "Allah" and "Ar-Rahman" when reciting the Basmala continuously?

"Lengthening" (al-madd) is intended to mean raising the voice, and it is possible that it means the natural lengthening (al-madd al-ṭabīʿī), and not the prolonged lengthening known to the reciters, because its prolongation beyond the natural lengthening is caused by the hamzah and sukūn. The ten reciters have agreed on this. It has been narrated from Anas that the recitation of the Prophet, peace and blessings be upon him, was with a lengthening, by which he prolonged his voice. Some have interpreted His saying, the Almighty: "Or add to it; and recite the Qur’an with measured recitation" (Qur’an 73:4) as recitation with deliberation and slowness, and that his recitation was a lengthening by which he prolonged "Bismillah" (In the name of Allah), "Ar-Rahman" (The Most Gracious), and "Ar-Rahim" (The Most Merciful). The lengthening in "Ar-Rahim" when stopping on it is an accidental lengthening due to sukūn, in which three facets are permissible.