Even removing the "per second" doesn't quite fix it; a data transfer speed can't be "equivalent" to simultaneously streaming N number of UHD videos; it may be equivalent to the speed necessary to simultaneously stream those N UHD videos.

It should be something like, "... will be capable of transmitting data at 144 terabits per second, roughly the speed necessary to simultaneously stream 5.76 million ultra-high definition videos."

Anyway, it was probably just a brain fart.

They assume that an average ultra-high definition video requires 25 megabit per second. Their max theoretical capacity is 144Tbps so the math is: 144Tbps/25Mbits = 5760000 (5.76 million simultanious video streams). Their wording might be confusing but their math is correct.