To what extent is what was reported about Ibn al-Mubarak true, that he used to pray 300 rak'ahs daily, taking into account that this takes approximately 20 hours, and where would the time remain for the rest of his deeds?

It is known that a single unit (rak'ah) fulfills its pillars and takes place with devotion in less than four minutes. It has been narrated from the Salaf (pious predecessors) that they prayed more than the aforementioned number of units in a day and night. Zaynu al-'Abidin, 'Ali ibn 'Abdullah ibn 'Abbas, and Mus'ab ibn Thabit all used to pray one thousand rak'ahs in a day and night. Imam Ahmad ibn Hanbal used to pray 300 rak'ahs before his illness, and then 150 rak'ahs after it. No specific number was authentically reported from Ibn al-Mubarak, but he was known for praying a great deal. The intended meaning of the "hastening of time" is the decrease of blessing in it. Allah blessed the time of the righteous, which manifested in the abundance of their prayers, teaching, and writings, despite their engagement in their daily lives.