You can't calculate it in a classical sense of compounded returns, since your return is a loss of more than 100%. When you compound a return you multiply the return with the previous return. If your return is negative number (more than 100% loss), and you multiply it with another negative, the math rules tells us that two negatives becomes a positive. Therefor your return is
undefinied.
Another way to see it is that when you lost your money and have 0 left, a loss then of another dollar, would mean an infinite loss, since you managed to lose 1 dollar out of no money. Therefor for you to be able to continue to lose money when at zero, it means that you actually had some type of dollar exposure that created that loss. That should be your base figure, not the 700.
You have to make up a new type of definition which is not a classical compounding of returns. 5700/25 = 228
(700-228)/700 -1 = 32.57% drop in value per year, but not a compounded drop, just the average drop out of the 700 starting.