to learn more about creating 3d font styles. see this page
The composite element creates a “nested” look. It is made from a border and an inner offset. The inner offset can be sunken , raised, or at the same level as the border:
sunken:

Raised:

Border:

The settings of “Composite element”

- Prefab – the base prefab for the offset element, all letter will be created with the specified prefab. Leave blank for default
- Translation – the translation of the element within the letter. You can use this to position the element relative to other elements
- Faces – use this to mask some parts of the mesh. For example , you can exclude the backface,sides or front face of the mesh.
- Face/Side Materials– Sets the material for the Faces , sides and bevel parts of the mesh
- Inner Face/Side Materials – Sets the material for the inner face, and the inner side of the element
- Face Uv Wrapping –
- Uniform – the same for all letters. Maps the material as a (0,0) to (1,1) square
- Stretch – stretches the material according to the letter size.
- Side Uv Wrapping – choose if you want to wrap sides along the u or v of the material.
- Shape Offset A/B – The larger offset is the offset of the the entire mesh. The lower offset is the offset the Raise/Sunken/Border part
- Z Size – the z size (or extrusion amount) for this element.
- Inner Z Size – set to 0 for a border effect. Set to a positive number for a sunken effect , and negative for raised effect. The size is specified in unity units
Real Life example
If you go to Extras/Font Packages/Themed/Blood you will find the following font:

Notice how the sunken effect makes the text look better. This is achieved using the composite font element:
