Respiratory particle fraction - what is it?

According to the Danish Work Authorities:

Respirable dust is the fraction of inhaled particles that reach the alveoli (part of the lung where gas exchange occurs) (some places designated as having a 50% cut-off at 4 µm) (reference to the cut-off: 

https://www.cdc.gov/niosh/docs/2014-151/pdfs/chapters/chapter-ae.pdf)

There are other regulatory relevant fractions too

Thoracic dust is the fraction of inhaled particles that passes the larynx (some places designated as having a 50% cut-off at 10 µm) (reference to the cut-off:

https://www.cdc.gov/niosh/docs/2014-151/pdfs/chapters/chapter-ae.pdf)

Inhalable dust is airborne particles that can be inhaled (by some designated as a cut-off of 100 µm)

(reference to the cut-off: https://www.cdc.gov/niosh/docs/2014-151/pdfs/chapters/chapter-ae.pdf)

Total dust is all sizes of dust collected with no pre-separator at an inlet speed of approximately 1.25 m/s 

The ICRP Publication 66 describes deposition of certain fractions of particles in the anatomical parts of the airways. I inserted the figure below

What confuses me is that it looks like in the alveoli particles of 10 µm (yes I like round numbers) seem to be deposited to a much smaller extent than the smaller 10 nm particles 

But then I calculated the numbers and they are 50 % for 10 nm particles (=500 µg of 1 m3 inhaled of a concentration of  1 mg/m3) while ~5% for 10 µm particles (=50 µg of 1 m3 of 1 mg/m3)