That screenshot shows values of the skill with effector equipped.
Also, the x42% means your defense is multiplied by 42% so it is maxing out at 42% of your full defense.
So, let's put here an example:
Your Defense: 5000
Maximum Defense: x42%
5000 * 42% = 5000 * 0.42 = 2100 will be your defense after using it.
So, to put it even simpler, with effector equipped it is -58% defense (on that screenshot), but default on official is still 70% which would mean Maximum Defense x30%.
I checked once more the defense values now, to make sure we did it correctly and this is what official has on the base skill:
XML:
<value bforce_id="5" bforce_value="-20,-300,0" power="" dur="0,18000" type="1" value_type="4" check_readiness="0" />
bforce_id="5" This one is the defense forceid
bforce_value="-20,-300,0" This is the combination of per level and base value of the skill, so -20 is the per level and -300 is the base value.
However, these values are also divided by 10 so it would mean that -2 per level and -30 base, so -2*20 will be -40 + -30 base, -70 at maximum level.
value_type="4" This one tells the game what kind of value it is, like a flat number or a percentage.
Hope this clears up some conspiracy