Isn't this set up on the product category under the Global Allocation settings?

I don't think, right now in all categories it is only checked "A", but i tried changing a random product to "R" and it still shows all the stock as available.

Should they all be checked?

Did you also check the allocation and issue rules?  Setup > Stock > Allocation rules
We have this set up with an allocation code that specifically calls out that only "A" is used.

Our set up

Mine's set up the same.

how should the allocation and issue rules under Setup > Stock > Allocation rules be configured to follow this rule?

Much appreciated sir.

Here is our allocation and issue rule set up.

Thank you sir, it seems our set up is just like yours, maybe i'm not properly asking.

I should have differentiated Available Stock from Total Stock.

Excuse my ignorance.

Are you trying to find something like this?

This is the Available Stock inquiry.  It can be run for each product.

Yes this is but now my coworkers are telling me they need something diferent, i will try to do it by myself but if i can't i will open a new post.

Thank you very much for your time sir.