So this is their key claim. There are several other claims made, but I'm speaking on what I know.
Internet speeds are usually measured in mega
bits per second (Mbps). A
bit is the smallest unit of data we typically work with.
These two articles refer to 1,976 mega
bytes being downloaded in 87 seconds, or approximately 22.7 mega
bytes per second.
For reference, there are eight
bits in one
byte. By the same scale, we can also say there are eight megabits in one megabyte.
One mega
bit is 1 million bits. So there are eight million bits in a mega
byte.
You follow me? Good.
It's actually pretty common to confuse mega
bits with mega
bytes; the distinction isn't really meaningful for most people.
However, if we're talking about something being "
IMPOSSIBLE"

then it is necessary to distinguish the two. Let's say this: the claim is that it is "impossible" to download data at 22.7 megabytes per second.
If we measure this by the standard measure of mega
bits per second (Mbps), 22.7 MB/s breaks down into 181.6 Mbps.
Guccifer 2.0 (who claimed credit for the hack) would have to have at least a connection speed of 181 Mbps. Is this "impossible"?