[adolph]

Kinda. To the degree that the object of increase is also a percentage the statement “increasing X (where x is quantified as a pct) by Y %” could mean that X of 20% is increased to 70% or to 30%. It would be more clear to state “X increases from Y% to Z%.”

[clipsy]

No, not kinda. In the example you present, if 20% increased to 70% the appropriate description is either a 250% increase or a 50pp ("percentage point"[0]) increase.

[0]: https://en.wikipedia.org/wiki/Percentage_point

[mtnGoat]

Math doesn’t do “kinda”. If you are paying $100 for something, and then it is $150, that’s is a 50% increase and is an undeniable fact.

[colecut]

20% to 70% would be quite the fee increase, but I suppose that is a way of thinking of it.