Misunderstanding of percentage increase [duplicate]
If something increases from $50$ to $200$, it increases by $300\%$ and has a new value that is $400\%$ of the old value.
Similarly, if something increases from $50$ to $52$, it increases by $4\%$ to a new value that is $104\%$ of the old one.
Percentage increase is $$\frac{\text{new number - old number}}{\text{old number}}\times 100 \%$$
The right comptuation should be $$\frac{200-50}{50} \times 100 \%=300\%$$