In the context of HOB spottings, what does "Air" signify?

In the context of HOB (Height of Burst) spottings, the term "Air" signifies that a round bursts in the air above the ground level. This is crucial in fire support coordination as it affects the shrapnel distribution and potential effectiveness of the round against the intended target. When the number of mils is specified, it provides additional information about the angle or degree of the burst's height, which is essential for adjusting fire and ensuring that subsequent rounds are accurately placed for maximum impact. This understanding of the airburst allows for strategic decisions on how to effectively engage targets without causing collateral damage, making it a fundamental concept in artillery and fire support operations.