How it is studied
Identification describes which botanical group can be recognised in a grain. Counting answers a different question: how many grains occur in a volume of air. A label such as Poaceae includes many species and does not identify which one produced each grain.
An example to interpret it
Unit example: 20 grains in a representative volume of 2 m³ would equal 10 grains/m³. This is a teaching calculation; an actual microscope slide also requires the factor for the area examined and the counting protocol.
What to check
This concentration does not tell you how many grains a person inhaled. Exposure depends on time, place and activity; an environmental figure is not a diagnosis.