What is the chance of getting anything while smashing rocks?

Question

What is the chance for getting things+pokemon, things, Pokemon? To make this more clear here is an example.(note non of them are right)
Like you will find or encounter something has 75% chance.
You will get an item has a 50% chance of 75%
You will encounter a Pokemon also has 50% chance of 75%
You will encounter specific item has a –% chance in 50% of the 75%
You will encounter specific Pokemon has a –% chance of 50% of 75%
Note: this is just an example. The answer should be like this but I don't think the parcentages I had put is accurate.

Comments

Still not a full answer, but https://bulbapedia.bulbagarden.net/wiki/User:Tiddlywinks/Breakable_rock

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it doesn't go off of chance. It pick one of 3 things happening

-Encounter a Pokemon
-Nothing happens
-Find an Item

items I have found are...

-Heart Scale x1
-Red Shard x1
-Green Shard x1
-Yellow Shard x4
-Old Amber x2
-Max Revive x1
-Blue Shard x1
-Helix Fossil x1

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Moving to a comment as this doesn’t really answer the question, sorry. There is almost certainly some probability to determine which of those options will occur, and if there isn’t you’d need to explain what process is used instead.

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It depends on what gen you are talking about.

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Still not a full answer, but https://sha.wn.zone/p/pokemon-encounter-rate