What does this mod do?

It corrects mathematics to acknowledge the fact that 2+2=🐟

What does that mean?

If you ever combine a stack of 2 with another stack of 2, the resulting stack of "four" (a mathematical fallacy) is replaced by 🐟. This sweeping correction will happen anywhere that items stack in the game: player inventories, chests, assembly machine inputs and outputs...

Does 3+1=🐟?

No; don't be ridiculous. Everyone knows that using an inserter with a stack size of 1 to add to a stack of 3 will result in a stack of quantity 4, not a 🐟.

Does 5-1=🐟?

Absolutely not. Withdrawing a single item from a stack of 5 only creates a stack of 4--literally children know this fact.

My machines keep exploding and dropping 🐟 everywhere and it's getting on my belt lines, which is very inconvenient. What can I do?

Be better. Use combinators and circuit logic to overcome the barriers that math itself poses.