Description of the Bug:
I went to make an Item Rarity Excluder potion, and the resulting potion came out at the wrong grade. My intention was to make a potion between 60 and 70 grade, so I did the math and found the right materials. The resulting potion came out 83 grade? You can see the grades of the materials I used in this screenshot:


Steps to reproduce:
I would assume the reproduction steps would be to craft an Item Rarity Excluder potion without using all g100 materials, do the math, and see what the result actually is. I'm not personally inclined to waste my remaining materials by trying it again and getting another potion I can't use. It seems like it's using an incorrect formula to generate the grade of the potion, possibly related to when the potion's recipe was changed months back (formerly used 2 flowers, 4 voxels, 1 varadium)

What should have happened?
The resulting potion should have been either 63 or 64 grade, per the math below
8 x 31 grade Voxel Fruit = 248
1 x 100 grade Aquamarine Stew = 100
2 x 100 grade Varadium = 200
4 x 100 grade Pumpkin Flower = 400
15 items, total grade = 948
average is 948 / 15 = 63.2

What did happen?
The potion result was 83 grade, too high.

My System:
PC, Windows 7, Firefox

Edit 4: Ok! So I've discovered some things. There's something wrong with the Item Rarity Excluder specifically. Ellix's calculation worked for every one of my tests except the Item Rarity Excluder. So I'm currently making more Item Rarity Excluders to check this out.

Edit 3: Jelly just brought to my attention the fact that basic ingredients add 100 to the calculation. I'll be revising all of my calculations shortly. ;v;

Edit 2: Actually, Ellix's theory doesn't explain some of the scenarios I came across. Potions like the Wealth Potion, Mass Range Extender, and Potion of Evolution all took into account the quantities of ingredients when the game calculated the final grade. It also doesn't explain why in some of my experiments, the game rounds down when it should've rounded up.

Edit 1: Ninja'd by Ellix xD

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So, I just want to start by saying that my assumption of the way the game calculates averages is the same as Chris'. I assume that the game adds up the grades of all ingredients used, and then divides that by the number of ingredients used (and ignores non-grade items, such as the Starch Cube and so on).

Based on that assumption, I tested every potion with varying grades of ingredients, starting with the Item Rarity Excluder. So if the game is supposed to calculate averages the way that we believe it is, then I can confirm that there's something wrong with the calculations for certain potions. Below are my results for every potion.

(Don't read this, it's wrong lmao)

..all of the above aside, the calculation looks correct if you ignore the quantity of the items and look at the individual items themselves.

1 item type grade 100
1 item type grade 100
1 item type grade 100
1 item type grade 31

Total types of items = 4
Total grades of item types = 331

331/4 = 82.75 rounded up becomes 83

So, can confirm what Elix said. Makes sense to me that it should work this way, considering that you can't mix item grades, it shouldn't matter what quantity of each item is required, just that there are x type of items being graded so they should sum as if the total item type quantity is 1