What does "chance to electrocute enemies" mean on a Rapid Shock Spike Shield?

What does "chance to electrocute enemies" mean on a Rapid Shock Spike Shield?

It lists three effects:

• Deals Shock Spike Damage to melee attackers.
• Chance to Electrocute enemies.
• Shock Spike Damage may Electrocute affected enemies.

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So, if I’m reading this right, some Shock Spike Shields might not electrocute enemies on being melee attacked, instead only electrocuting with the Shock Spike Damage?

And then Fire and Corrosive ones don’t seem to have 3 lines like that, even though each of them have their own elemental damage over time?