A carpenter is building two types of tables: small tables and large tables. Each small table requires 4 hours to build, and each large table requires 7 hours to build. The total time spent building tables is 180 hours. The equation $4s+7L=180$ represents this situation, where $s$ is the number of small tables built and $L$ is the number of large tables built. Which statement is the best interpretation of $4s$ in this context?