The bottom line ( ie x axis ) is airflow, looks like kg/s

But what you want, and what air your engine will consume arent always the same thing.

Just because the chart doesnt show any lower doesnt mean you cant use it though.
Oddly the compressor map from Vortech for my blower doesnt show anything higher than about 40,000rpm

Weird because nobody would ever turn it that slow, some even spin it at 80k !