From the video: 4.4k is "almost" 4x times 1.8k because 4.4k has "number 4" in the beginning, and the other one - number 1.

For the lazy: that's less then 3x: 1.8 * 3 = 5.4

It’s not even the largest part, just prefill so I think maybe M5 Max is 30% faster overall. Still pretty good I think but the 4x nonsense is just marketing!