The core repository uses Web3-Units to manage the different units utilized by the protocol. There are often conversions between decimals, floats, integers, fixed point integers, wei, and percentages. Without the unit library, these values would often be of type BigNumberish, making it very easy to use a value that is in the wrong units.
• FixedX64: The Engine contract uses the ABDK64x64 math library, a fixed point number library that stores the numerator of a value in an int128. All the denominators of these values are 2^64, thus 64x64. This class type gives us easy getters to convert the raw numerator value into a regular value, by dividing by this denominator.