Okay as we all know, Covenant Ships are only building level going by this scene
Since Halo sucks, I will assume it is only the minimum of building level, or .25 tons of TNT
Also, since cinematic timing is BS, I will assume it took the length of the whole mission to destroy it. Or 5 minutes (That is how long I could stand the game)
So it has a power output of 3,486,666.67 watts.
Now it takes 30 years for the Covenant to glass the surface of the Earth. As a highball I will assume it meant the hole crust. It also said it needed a full fleet, since 500 ships is wank. I will assume it took the amount of ships of the entire Covenant. Or only 3000.
I get 9.90256338e18 joules to do that.
Now melting it would be wanking, I will assume they only pulverized it.
Thus I only get 4.59835773e13 liters.
The crust is 1% of the Earth. So the entire Earth is 4.59835773e15 liters.
I only get 12.8 Miles, which is very consistent.
As you see, Halo's Earth is only the size of an island.
So as you see Halo wankers, the UNSC is extremely weak, I bet the Halo Galaxy is not even a lightyear big