The Bhu-Mandala Universe is also known as the ''Greater Earth Mandala" a universal expanse that looks like a flat disc of planets which includes the entire 14 different Planetary Systems.
This large ''Earth Mandala flat disc of planets'' are not to be confused with our ''small Earth Mandala'' globe we live on.
Therefore there are two Earth Mandala descriptions in Srimad Bhagavatam
1 - "The large Earth Mandala" called Bhu-Mandala which is our entire 6 billion 438 million kilometres in diameter Universe.
2 - "The small Earth Mandala" which is our round Earth global sphere which is a small Planet in space that has a diameter of 12,742 Kilometres and is in the middle Planetary System as shown in the photo of the 14 Planetary Systems which is the Bhu-Mandala Universe.
So the Bhu-Mandala Universe is the "greater Earth Mandala" that is 6 billion 438 million kilometers in diameter and is the size of our small universe.
The "smaller Earth Mandala" or our round Earth global sphere is just 12,742 kilometers in diameter therefore our small Earth is NOT the greater Earth Bhu-Mandala.
Srila Prabhupada - "Within this material energy there are innumerable universes, in every universe there are innumerable material planets, and the earth is one of these planets. Thus we can understand what an insignificant part of the entire cosmos is this globe on which we live''. (Light of the Bhāgavata 47)
Srila Prabhupada - ''Dvipas (islands) are planets in outer space'' (CC Madhya 20.218)
Srila Prabhupada - ''The floating of the planets in the weightless air is due to the inner constitution of the globes, and the modernized drilling of the earth to exploit oil from within is a sort of disturbance by the modern demons and can result in a greatly harmful reaction to the floating condition of the earth''. Srimad Bhagavatam Canto 2 Chapter 7 Text 1
Srila Prabhupada - ''Just like here, in this planet you see flat, when you go up, you see it is ball. But when you go up you see just like a ball.” (Lectures, Bhagavad-gita 2.12, Bhagavad-gita 2.12, New York, March 9, 1966)
The circumference of our earth globe around the equator is 40,075 km and the Earth"s diameter is 12,742 km.
So NO WAY is our small Earth globe Bhu-Mandala which is way to big to be our small Earth globe which is described in Srimad Bhagavatam's 5th Canto as being -
6 billion 438 million kilometers in diameter.
And almost 20 billion kilometers in circumference.
This just happens to be the size also of our entire small Universe that is deep within and surrounded by a bigger Brahmanda egg shaped Universe that comes from Maha Vishnu with billions of other Brahmandas in all different sizes.
Our Brahmanda is massive being 71 Quadrillion 715 Trillion 715 billion kilometers in diameter and having a circumference of almost 242 Quadrillion kilometers
So keep in mind that Islands mention in this chapter of Srimad Bhagavatam really means global planets in outer space like our earth planet
Srila Prabhupada - ''Just like here, in this planet you see flat, when you go up, you see it is ball. But when you go up you see just like a ball.” (Lectures, Bhagavad-gita 2.12, Bhagavad-gita 2.12, New York, March 9, 1966)''