Salem

Trying to get Leather with the help of http://salemwiki.info/index.php/Leather
For the first time i got 1 Leather and 3 limed hides of 99% readiness (using BD salem atm)
For the second time got 3 Leather and 1 limed hide 99%

I see that there is a sign in the article about crafting Leather :

* - There is currently a possible bug in the game where if you place 4 limed hides before you add the liquid, then just one 10L bucket of tanning fluid is all that's required to turn all 4 hides into leather

So ...at last ... could someone tell me how many leather pieces should i get each time?

You have to put the limed hides in BEFORE the tanning fluid is put in, as soon as the tanning fluid starts to work on one hide it ticks down how ever if all the hides are in at the same time they all tick down at the same time. So for your second batch you simply were able to put your hides in faster meaning that 3 thicked down before the fourth was placed in the fluid.

The problem is that i had put 4 limed hides before adding tanning fluid for the first time and for the second time. I'm absolutely sure.
Also when i had 3 limed hides with 99% readiness in the tanning tub i tried to add tanning fluid. As the result i got 1 leather immediately and 2 limed hides stayed like they had been before adding fluid.
Mystery?

Each hide requires 10 litres of tanning liquid.
So if you put 4 hides and 10 litres of tanning liquid then 1 hide will become leather and 3 others won't change.
I assume that second time you poured 30 litres of tanning liquid into the tube, which made 3 hides turn into leather.

This is a known thing, but no comment from the devs on what the bug actually is.

What isn't known: should the tub always use 10 L of fluid per hide so that if you have 4 hides you only get 1 hide per 10L of fluid in the tub? Should it work "as is" but instead of sucking out all the fluid you still get 4 hides for 10 L, but each hide only needs 2.5L of fluid to process? (Note: It's been a while since I tested, but I believe even with just 1 hide and 20 L of fluid, it still sucks up all the fluid.)

edit: fixed post so appropriate to previous replies