What is the meaning of the Hadith: "There will remain in Paradise what Allah wills to remain, then Allah Almighty will create for it a creation of whatever He wills"?

The aforementioned Hadith indicates the immense power of Allah, His mercy, and the vastness of Paradise and Hell, and that each of them will be filled. Hell will be filled when Allah places His Foot in it, whereupon it will shrink and be completed. As for Paradise, there will remain a surplus after its inhabitants have entered it, so Allah will create a new creation for it and admit them into it. This is evidence of Allah's grace and that reward is not contingent solely on deeds. For Allah creates peoples and admits them into Paradise by His grace without any deeds from them, as is the case with children and the insane, which demonstrates the immense vastness of Paradise.