A blue or magenta number pair shown near airspace boundaries (e.g., '100/80' or '55/SFC') represents:
AThe ceiling and floor of the airspace segment, in hundreds of feet MSL (with SFC meaning 'surface')✓ Correct answer
BThe runway heading and magnetic variation
CThe LAANC grid maximum altitude values
Why →Number pairs on sectional airspace boundaries represent the ceiling and floor of that airspace segment, always in hundreds of feet MSL. '100/80' means ceiling 10,000 feet MSL, floor 8,000 feet MSL. '55/SFC' means ceiling 5,500 feet MSL, floor at the surface. This pattern applies to Class B shelves, Class C shelves, and some Class D configurations.
The trap →Number pairs can look like frequencies to a new reader. The slash and the hundreds-of-feet convention identify them.
Field note →Read the pair top-to-bottom as ceiling-over-floor. 'SFC' always means surface, not a numeric value.