IIC, IIIC, etc.

In our Canadian soil classification system, there are many additional descriptions (and associated suffixes and prefixes) of soil horizons, besides those mentioned in your lab manual & my online lecture notes. Those Roman numerals, shown as prefixes, are one of those examples that we skipped in this course.
Since they are not explained in lecture and/or lab, you can skip them in your explanation too.

I'll provide here a simplified explanation of the Roman numerals, but this is NOT of relevance for our Introduction course. So, read it if you are interested, but otherwise pls ignore.
Roman numerals indicate lythological discontinuity within the soil profile. This lythological discontinuity is due to a different mode of deposition, which means that some soils will have horizons that have formed on different types of parent materials, and those parent materials got deposited on the top of each other.