[1] https://www.figma.com/blog/webassembly-cut-figmas-load-time-...
What they did was cutting it to 30% or by 70%.
newLoadTime = oldLoadTime - (70% of oldLoadTime)
newLoadTime = oldLoadTime / 3
Personally I find the additive expression unintuitive and find the multiplicative expression easier to reason about. "cut by" does generally indicate an additive expression. It should really have been phrased as something like "reduced by a factor of 3"
Factor, noun "a number or quantity that when multiplied with another produces a given number or expression."
It's not an exact integer factor, but I think the concept of factor is more general than that.
That would imply the phrase has to be "reduced by a factor of 1/3", which leads to the wrong impression. The better technically correct phrase would be "reduced by a divisor of 3"