Difference between PM2.5 and 2.5 micron in the particle counter test value?

What is difference between PM 2.5 and 2.5μm in the particle counter test value?  Isn't PM2.5 = 2.5μm?
The 0.3μm and 2.5μm is number of particles.

PM2.5 and pm10 is the weight of particles.

two different value unit can exchange in one machine.

 

 

So PM2.5 ≠2.5μm

 

when use the handheld particle counter test out value in the screen.general just see the PM2.5 is ok,

boz this is the International unit standard to see the air quality is good or bad.