Short explanation. These are additional modifiers of the dimension being cut. The surplus increases it by a set value on each side of the element. The margin, on the other hand, decreases the dimension.

Longer explanation. Surplus and margin must not be confused with gross and net dimensions. If the element is to be increased due to veneering, go to the material group and select that the gross dimension is to be cut. So what is the purpose of the surplus and the margin? These are some examples of use:

• If, after the cutting, the resulting edges are not ideal and require further processing, we must cut somewhat larger elements. This is what the surplus is for.
• If we want larger dimensions on the labels than the actual element dimensions, we must use the margin.

Curious fact. You can set default surplus and margin values in the material group settings. If so, both values will already be set when adding new elements. We can also force specific values so that they cannot be changed while adding elements.