Final answer:
The air traffic controller is giving the position and distance of the other aircraft using a clock face analogy.
Step-by-step explanation:
When the air traffic controller states "10 O'CLOCK 3 MILES," they are referring to the position of the other aircraft relative to the direction the CESSNA GPTO is facing. The controller is using the analogy of a clock face, where 12 o'clock represents the nose of the CESSNA GPTO, and the other positions are relative to that.
In this case, the other aircraft is at 10 o'clock, which means it is on the left-hand side and slightly above the CESSNA GPTO. The 3 miles distance indicates how far away the other aircraft is from the CESSNA GPTO.