For a spring class at Theresa Banks Pool, the facility doesn't have a section under the activity on PARKS DIRECT. Since the season (spring) and location (Theresa Banks Pool) are unique to the section, you can ignore sections that don't start with section code 283. In the section code, 2 is the season number for spring, and 83 is the location number for Theresa Banks Pool. 

Because the section for your activity doesn't already exist, you can create the section with section code 283A for the spring class at Theresa Banks Pool.

The section code, 283A, breaks down into its three parts: season, location, and section letter.

Spring [2]  Theresa Banks Pool [83]  No existing sections for my location [A] 

Soon after making the first section, 283A, you realize that you need two additional sections of the same activity! The next two section codes you need to create are 283B and 283C.