What is the exact effect of the Pass Power on Hidden Grottoes?

Question

Okay so I recently decided to catch every HG Pokémon there is in W2 and learned that the HG Pass Power can increase the odds of one generating. The thing is, what are the exact odds of a HG generating every 256 steps with the lowest Pass Power on?

Comments

"For every 256 steps taken, there is a 5% chance a Hidden Grotto will regenerate; if a Pass Power is used, the chances will increase. When they do regenerate, this is a 40% chance of there being an item, a 40% chance of there being a hidden item, and a 20% chance of there being a Pokemon"

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This was not exactly helpful since I knew the base odds already but thanks for trying anyhow :)

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Want me to convert this to a comment since it doesn't help?

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@PokeFanatic In case you didn't know, converting this answer to a comment puts your question on the unanswered list, which increases the chance that someone else will see it and post a better answer.

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Sure. I mean I am still new here so that would be really helpful