It used to say "minimum" instead of "up to" .
When i saw it the first time i actually thought they probably made a mistake because it would imply if i had a 4mbit/s line i -can- get 4 mbit/s on the cheapest package (and why would anyone bother with any other package if that was true?). Not even Telkom can guarentee you a "minimum" speed, and i doubt they have such a clause anywhere. They only state the MAX.
So from a business/economic standpoint i knew there's no way they can logically offer a "minimum" , it just does not make any business sense

.
However it did make me reconsider when i had to choose between Screamer vs Digichilli. Screamer have a "up to 384" package which are R100 more expensive, and DC's wording of "minimum of 256" implied i would most likely get the same speeds as on Screamer as the 256 is only the "minimum" (thus i could "burst" to 384 if the network allows)
But after some common-sense thinking about this, i realised it must be a grammar error, because no one , not even Vodacom/MTN with their 7.2 Mbit/s connections will tell you you will get a "minimum" speed of even as low as 256 kbps. That would be shooting yourself in the foot.