I think you are off on your powers of ten here. “Peta” is a metric prefix for 10^15. One quintillionth would be 10^-18 (millionth is 10^-6, billionth is 10^-9, trillionth is 10^-12, quadrillionth is 10^-15 — I personally had to work it out that way to make sure I got it right.)
So 2 PW is 2x10^15W. 25 quintillinths of a second is 25x10^-18. The energy released is thus the product of these or 50x10-3J. This is equivalent then to 0.05W for 1 second.
Doh, my bad. Just realized that my brain was somehow reading a capital “M” in your answer rather than the lowercase “m” that was actually there. Your calculation is of course absolutely right. My apologies.