It is called " junk"
The number left over in a division problem is called the "remainder".
stray
Your question isn't fully clear, but if you are referring to the process of division of numbers, the "number left over" is called a remainder.
Those materials left over after the economically extractable portion of the mineral being mined has been separated from the ore.
The left over fruit material is called pulp.
solifluction
Disposable income.
The remainder.
The left side of a chemical equation is called the reactant side when balancing the equation. This side contains the starting materials that participate in the reaction.
Materials that decompose can be used to plant other foods. Materials that do not decompose have paper, peeling and left over foods in it.
Remnants
A Surplus