60% larger... and 500% more massive
...Huh?
1.6 times Earth's radius. Volume and mass are proportional to the cube of the radius.
Sort of, but not quite. Indeed in this case "60% larger" is talking about its radius (which is a weird way of putting it) but assuming a straightforward mass ∝ radius^3 relationship would imply the planet is 4.3 times* more massive, not five times. This is because planets of different sizes are also likely to have different densities, so while volume is proportional to radius cubed, mass is not exactly proportional to volume.
The "5 times more massive" thing actually has fairly big error bars, but it's the best estimate they have based on probable composition.
*(1.63^3, 1.63 being the best number I could find for the radius relative to Earth's)