Those are static pressure (SP) adjustments. Static pressure is a confusing sounding term for resistance to flow. For example, if you put a 90 elbow turn in the duct, that causes a resistance to flow.
CFM @ 0.000-In. SP 1005 means: 0.000 static pressure, i.e., if there is nothing creating any resistance to the flow... then the fan can pull 1005 cubic foot of air through the pipe, per minute.
CFM @ 1.250-In. SP 480 means 1.250 static pressure (measured in inches -In.), ie., if there is that much resistance to the flow... the fan can pull only 480 cubic foot of air through the duct, per minute.
You would have to do a static pressure calculation based on duct size, material, turns radius and locations, reductions, and duct length -- and the result would be a The SP#... then look for the number on that table and it will tell you what to expect that fan to be able to pull through it, in CFM.
Mike and Dale have that all written out somewhere... how to do the calcs and what to use... I'm not sure where though.
Me
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