Reducing error by 25% from a 96.5% baseline gives you their stated 97.25% accuracy. About 0.75% fewer errors. Still amazing, but less impressive than the abstract makes it sound.
Actually, 25% is the right way to judge this improvement. For example, let's say performance was currently at 99.9% and you improve it to 99.99%. That's not a 0.09% improvement (99.99 - 99.9), but rather a ten-fold improvement (.01% errors vs 0.1% errors).
This has to do with the fact that accuracy/errors are not linear.