Edit: the original image got lost to time, replaced with the closest equivalents I had in my archives.
 

Various parts of the message are changed from the original, the one that stands out being the fact that the “man” is replaced with a “pony”.

The total list of changes:
>what DNA is made out of
>How that DNA is layed out
>How many base pairs in chromosome
>Ponies, not humans
>How high ponies are
>Population number
>Planetary system, indicating that there is one sun and two planets, or possibly one planet and one moon. The message is sent from the smaller “planet”.
>Shape of radio used to send the message
>Radio dish’s diameter

– source

>1. Numbers
Identical to the human number system.

>2. DNA
Unlike humans, this DNA structure is made of Scandium, Zinc, Vanadium, Oxygen and Gallium.

>3. Nucleotides
These are going to take some time to crack, so I’ll just skip them now. But they’re not human.

>4. Double Helix
Assuming this is supposed to be pony DNA, they also use the double helix structure, but it’s once again different from humans.

>5. Humanity/Equinity
The figure in the middle of element 5 is a pony. The bar directly left of the figure is multiplied by 126 mm and does in the human version display the average height of a male human. Here it gives us a presumed height of 1.638 m.
They’re tiny horses, who would have known?
On the other side, we have the population count. According to this, Equestria has a population of 4 292 214 766, almost exactly the same Earth had in 1974.

>6. Planets
This is a bit open to interpretation. That big square to the left is probably Equestria’s sun, and the one furthest right (the small one that the pony is “standing on”) is Equestria. The one in the middle might imply that Equestria’s solar system has only two planets, and that there is something like a gas giant between their sun and Equestria. However, it does not follow the “rules” for how planets are represented in the Arecibo message. A larger planet should be a longer vertical line, not a square. In fact, it looks like a smaller sun.
So Equestria either has two suns or, as I believe, that smaller “sun” represents Equestria’s moon. The Sun, the Moon and Equestria are the only things in their solar system.

>7. Telescope
In the human version, this is a figure of the telescope we sent this from. Here, however, we see whatever Luna broadcasts with. Kind of looks like Apollo 15’s subsattelite, which would fit the uplink frequency show on the transmission submit thingy on the blog. If I’m reading the end correctly, the diameter of her broadcaster is 1.512 m.
There may be more in here, but that’s all I had time for right now.

– source