"Static flow" rate is the flow in units of quantity per unit of time with the injector held open. The 280 and 292 values are the flow in cc/min (cubic centimeters per minute)--divide cc/min by 10.5 to estimate the flow in lbs/hour (pounds per hour).
Gasoline weighs 6.073 to 6.2 lbs per gallon (87 to 93 octane);
one gallon = 3785.4 cc,--therefore 1 cc = 0.00026417 gallon = 0.0016043 pounds (87 octane);
1 cc/min (87 octane) = 0.0962583 lbs/hour (0.0016403 * 60);
292 cc/min = 28.1 lbs/hour (292 *0.0962583) (87 octane)
It looks like Injector ℞ used 6.0 lbs/gallon--close enough...
At 6.0 lbs/gallon, 1 cc/min = 0.0951012 lbs/hour; * 292 = 27.7695 lbs/hour.