A 4x increase is a 300% increase, not 400%. Otherwise a 100% increase would mean an increase of a multiple of 1...
People must be careful of the terminology used.
What was the original terminology used? "There was a 4x increase in sales?" If so, then...
A 4x increase is a 400% increase, to my mind.
I interpret that to mean that the *increase* was 4x of the original.
X = 100
4x Increase -> 4*100 = Increase of 400
Y = 100 + 400 = 500
If you intend to state that the new amount is 4x higher than the original amount, that would indeed be a 300% increase, and I would use terminology more like this: "The new amount is 4x higher than the original amount".
X = 100
4x Higher -> 4*100 = New Amount of 400
Y = 400
A lot of the times, these kinds of "this percent increase" or "that times this" etc. are states ambiguously or incorrectly because the terminology used doesn't mean what they think it means. I choose to interpret literally, whether that's what they intended or not. I ask again, what was the original terminology used?
I just found the article. He said this: "That has had a 4x lift on our hardware sales."
Lift is a synonym for "increase", so I interpret this as follows: "Hardware sales increased by 4x".
Mathematically:
X = Original = 100
Y = New = Original + Increase
Z = Increase = X * 4 = 100 * 4 = 400
Y = X + Z = 100 + 400 = 500
Which is a 400% increase.
Now, I have no way of knowing if that's what he *meant* or not.
Because if hardware sales were doubled, that would mean 100 became 200, which is a 100% increase, otherwise known as a 1x increase, which I doubt he would have said.
So it's likely he meant "That resulted in a 4x greater sales total for our hardware." Which is a sentence with a different meaning than his original sentence, but which I think we can reasonably infer that he probably meant instead.
Again, it's a semantic problem with the way people use these mathematical terms. There are multiple ways to represent differences in data, and often people use the wrong terminology and end up giving a different impression than what is really intended, and very few people besides me ever seem to actually notice these ambiguities haha.