Math formula for calculate the profit/loss

I know that in Forex, the profit/loss is proportional to difference between the entry and out, and that lot is the constant of proportionality.

So, however, I found these formulas in a broker of bitcoins, and the despite of the reliability of bitcoins and of brokers of bitcoins, I was intrigued with the math formula for calculate the profit. This formula is not linear, the profit is not proportional to difference between the entry and out. This really makes sense? Is it correct? Why the profit/loss in Forex is not like this?

I await more clarification! Thank!