The Measurement Should Be Conducted Repeatedly
When the measured value well below average, i.e. 50 percentile, most parents falter and immediately wants to do something about the situation. This is obviously wrong, the results of a growth chart from one measurement but not too overrated. Far more important is the fact, as the chart located points that represent the repeated measurements of the child, respectively.
Impressions formed a line connecting them. In the ideal case would be approximately track the progress of lines that are shown in the graph, and should not be compared to them or not rise or even fall - it would mean a growth disorder. Therefore, the measurement should be conducted repeatedly and at regular intervals to determine whether there is really a failure of growth it or not.
Every child is a different growth rate, and therefore cannot be from one measurement to draw any serious conclusions. But if you find that...